curlx: use curlx allocators in non-memdebug builds (Windows)

To limit raw allocators to `CURLDEBUG` (memdebug/TrackMemory) Windows
UNICODE builds.

Closes #19788
diff --git a/lib/curlx/fopen.c b/lib/curlx/fopen.c
index caf4978..1838b7d 100644
--- a/lib/curlx/fopen.c
+++ b/lib/curlx/fopen.c
@@ -100,8 +100,7 @@
     goto cleanup;
   if(!needed || needed >= max_path_len)
     goto cleanup;
-  /* !checksrc! disable BANNEDFUNC 1 */
-  ibuf = malloc(needed * sizeof(wchar_t));
+  ibuf = CURLX_MALLOC(needed * sizeof(wchar_t));
   if(!ibuf)
     goto cleanup;
   if(mbstowcs_s(&count, ibuf, needed, in, needed - 1))
@@ -122,8 +121,7 @@
   /* skip paths that are not excessive and do not need modification */
   if(needed <= MAX_PATH)
     goto cleanup;
-  /* !checksrc! disable BANNEDFUNC 1 */
-  fbuf = malloc(needed * sizeof(wchar_t));
+  fbuf = CURLX_MALLOC(needed * sizeof(wchar_t));
   if(!fbuf)
     goto cleanup;
   count = (size_t)GetFullPathNameW(in_w, (DWORD)needed, fbuf, NULL);
@@ -156,19 +154,16 @@
       if(needed > max_path_len)
         goto cleanup;
 
-      /* !checksrc! disable BANNEDFUNC 1 */
-      temp = malloc(needed * sizeof(wchar_t));
+      temp = CURLX_MALLOC(needed * sizeof(wchar_t));
       if(!temp)
         goto cleanup;
 
       if(wcsncpy_s(temp, needed, L"\\\\?\\UNC\\", 8)) {
-        /* !checksrc! disable BANNEDFUNC 1 */
-        free(temp);
+        CURLX_FREE(temp);
         goto cleanup;
       }
       if(wcscpy_s(temp + 8, needed, fbuf + 2)) {
-        /* !checksrc! disable BANNEDFUNC 1 */
-        free(temp);
+        CURLX_FREE(temp);
         goto cleanup;
       }
     }
@@ -178,25 +173,21 @@
       if(needed > max_path_len)
         goto cleanup;
 
-      /* !checksrc! disable BANNEDFUNC 1 */
-      temp = malloc(needed * sizeof(wchar_t));
+      temp = CURLX_MALLOC(needed * sizeof(wchar_t));
       if(!temp)
         goto cleanup;
 
       if(wcsncpy_s(temp, needed, L"\\\\?\\", 4)) {
-        /* !checksrc! disable BANNEDFUNC 1 */
-        free(temp);
+        CURLX_FREE(temp);
         goto cleanup;
       }
       if(wcscpy_s(temp + 4, needed, fbuf)) {
-        /* !checksrc! disable BANNEDFUNC 1 */
-        free(temp);
+        CURLX_FREE(temp);
         goto cleanup;
       }
     }
 
-    /* !checksrc! disable BANNEDFUNC 1 */
-    free(fbuf);
+    CURLX_FREE(fbuf);
     fbuf = temp;
   }
 
@@ -206,8 +197,7 @@
     goto cleanup;
   if(!needed || needed >= max_path_len)
     goto cleanup;
-  /* !checksrc! disable BANNEDFUNC 1 */
-  obuf = malloc(needed);
+  obuf = CURLX_MALLOC(needed);
   if(!obuf)
     goto cleanup;
   if(wcstombs_s(&count, obuf, needed, fbuf, needed - 1))
@@ -222,12 +212,10 @@
 #endif
 
 cleanup:
-  /* !checksrc! disable BANNEDFUNC 1 */
-  free(fbuf);
+  CURLX_FREE(fbuf);
 #ifndef _UNICODE
-  /* !checksrc! disable BANNEDFUNC 2 */
-  free(ibuf);
-  free(obuf);
+  CURLX_FREE(ibuf);
+  CURLX_FREE(obuf);
 #endif
   return *out ? true : false;
 }
@@ -269,8 +257,7 @@
   errno = _sopen_s(&result, target, oflag, _SH_DENYNO, pmode);
 #endif
 
-  /* !checksrc! disable BANNEDFUNC 1 */
-  free(fixed);
+  CURLX_FREE(fixed);
   return result;
 }
 
@@ -303,8 +290,7 @@
   errno = fopen_s(&result, target, mode);
 #endif
 
-  /* !checksrc! disable BANNEDFUNC 1 */
-  free(fixed);
+  CURLX_FREE(fixed);
   return result;
 }
 
@@ -342,8 +328,7 @@
   errno = freopen_s(&result, target, mode, fp);
 #endif
 
-  /* !checksrc! disable BANNEDFUNC 1 */
-  free(fixed);
+  CURLX_FREE(fixed);
   return result;
 }
 
@@ -382,8 +367,7 @@
 #endif
 #endif
 
-  /* !checksrc! disable BANNEDFUNC 1 */
-  free(fixed);
+  CURLX_FREE(fixed);
   return result;
 }
 
diff --git a/lib/curlx/multibyte.c b/lib/curlx/multibyte.c
index 2583f30..fb3b7be 100644
--- a/lib/curlx/multibyte.c
+++ b/lib/curlx/multibyte.c
@@ -45,13 +45,11 @@
     int str_w_len = MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS,
                                         str_utf8, -1, NULL, 0);
     if(str_w_len > 0) {
-      /* !checksrc! disable BANNEDFUNC 1 */
-      str_w = malloc(str_w_len * sizeof(wchar_t));
+      str_w = CURLX_MALLOC(str_w_len * sizeof(wchar_t));
       if(str_w) {
         if(MultiByteToWideChar(CP_UTF8, 0, str_utf8, -1, str_w,
                                str_w_len) == 0) {
-          /* !checksrc! disable BANNEDFUNC 1 */
-          free(str_w);
+          CURLX_FREE(str_w);
           return NULL;
         }
       }
@@ -69,13 +67,11 @@
     int bytes = WideCharToMultiByte(CP_UTF8, 0, str_w, -1,
                                     NULL, 0, NULL, NULL);
     if(bytes > 0) {
-      /* !checksrc! disable BANNEDFUNC 1 */
-      str_utf8 = malloc(bytes);
+      str_utf8 = CURLX_MALLOC(bytes);
       if(str_utf8) {
         if(WideCharToMultiByte(CP_UTF8, 0, str_w, -1, str_utf8, bytes,
                                NULL, NULL) == 0) {
-          /* !checksrc! disable BANNEDFUNC 1 */
-          free(str_utf8);
+          CURLX_FREE(str_utf8);
           return NULL;
         }
       }
diff --git a/lib/curlx/multibyte.h b/lib/curlx/multibyte.h
index fac07c2..3eae4e7 100644
--- a/lib/curlx/multibyte.h
+++ b/lib/curlx/multibyte.h
@@ -44,12 +44,20 @@
  * memory tracker memdebug functions.
  */
 
+#ifdef CURLDEBUG
+#define CURLX_MALLOC(x) malloc(x)
+#define CURLX_FREE(x)   free(x)
+#else
+#define CURLX_MALLOC(x) curlx_malloc(x)
+#define CURLX_FREE(x)   curlx_free(x)
+#endif
+
 /* MultiByte conversions using Windows kernel32 library. */
 wchar_t *curlx_convert_UTF8_to_wchar(const char *str_utf8);
 char *curlx_convert_wchar_to_UTF8(const wchar_t *str_w);
 
 /* the purpose of this macro is to free() without being traced by memdebug */
-#define curlx_unicodefree(ptr) free(ptr)
+#define curlx_unicodefree(ptr) CURLX_FREE(ptr)
 
 #ifdef UNICODE
 
@@ -65,8 +73,13 @@
 
 #else /* !UNICODE */
 
+#ifdef CURLDEBUG
 #define curlx_convert_UTF8_to_tchar(ptr) _strdup(ptr)
 #define curlx_convert_tchar_to_UTF8(ptr) _strdup(ptr)
+#else
+#define curlx_convert_UTF8_to_tchar(ptr) curlx_strdup(ptr)
+#define curlx_convert_tchar_to_UTF8(ptr) curlx_strdup(ptr)
+#endif
 
 typedef union {
   char                *tchar_ptr;