Rename p_thread_callback_base to p_thread_callback_boringssl.

This fixes the Windows build. Otherwise this collides with the symbol in
Chromium's //base. (The 'base' suffix is the name of the library, not some
Windows-ism.)

Change-Id: I65d755f08991978bd2040d53c401082b2fee65fa
Reviewed-on: https://boringssl-review.googlesource.com/4217
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/crypto/thread_win.c b/crypto/thread_win.c
index ee48f34..240444f 100644
--- a/crypto/thread_win.c
+++ b/crypto/thread_win.c
@@ -127,14 +127,14 @@
  *
  * Force a reference to _tls_used to make the linker create the TLS directory
  * if it's not already there. (E.g. if __declspec(thread) is not used). Force
- * a reference to p_thread_callback_base to prevent whole program optimization
- * from discarding the variable. */
+ * a reference to p_thread_callback_boringssl to prevent whole program
+ * optimization from discarding the variable. */
 #ifdef _WIN64
 #pragma comment(linker, "/INCLUDE:_tls_used")
-#pragma comment(linker, "/INCLUDE:p_thread_callback_base")
+#pragma comment(linker, "/INCLUDE:p_thread_callback_boringssl")
 #else
 #pragma comment(linker, "/INCLUDE:__tls_used")
-#pragma comment(linker, "/INCLUDE:_p_thread_callback_base")
+#pragma comment(linker, "/INCLUDE:_p_thread_callback_boringssl")
 #endif
 
 /* .CRT$XLA to .CRT$XLZ is an array of PIMAGE_TLS_CALLBACK pointers that are
@@ -149,7 +149,7 @@
  *
  * See VC\crt\src\tlssup.c for reference. */
 
-/* The linker must not discard p_thread_callback_base. (We force a reference
+/* The linker must not discard p_thread_callback_boringssl. (We force a reference
  * to this variable with a linker /INCLUDE:symbol pragma to ensure that.) If
  * this variable is discarded, the OnThreadExit function will never be
  * called. */
@@ -159,15 +159,15 @@
 #pragma const_seg(".CRT$XLC")
 /* When defining a const variable, it must have external linkage to be sure the
  * linker doesn't discard it. */
-extern const PIMAGE_TLS_CALLBACK p_thread_callback_base;
-const PIMAGE_TLS_CALLBACK p_thread_callback_base = thread_local_destructor;
+extern const PIMAGE_TLS_CALLBACK p_thread_callback_boringssl;
+const PIMAGE_TLS_CALLBACK p_thread_callback_boringssl = thread_local_destructor;
 /* Reset the default section. */
 #pragma const_seg()
 
 #else
 
 #pragma data_seg(".CRT$XLC")
-PIMAGE_TLS_CALLBACK p_thread_callback_base = thread_local_destructor;
+PIMAGE_TLS_CALLBACK p_thread_callback_boringssl = thread_local_destructor;
 /* Reset the default section. */
 #pragma data_seg()