Fix VS2010 compilation

Avoid C99 style declaration (MSVC)
diff --git a/expat/lib/xmlparse.c b/expat/lib/xmlparse.c
index e308c79..2d0bd3b 100644
--- a/expat/lib/xmlparse.c
+++ b/expat/lib/xmlparse.c
@@ -1693,14 +1693,16 @@
   }
 
   if (len > bufferLim - bufferEnd) {
+#ifdef XML_CONTEXT_BYTES
+    int keep;
+#endif  /* defined XML_CONTEXT_BYTES */
     int neededSize = len + (int)(bufferEnd - bufferPtr);
     if (neededSize < 0) {
       errorCode = XML_ERROR_NO_MEMORY;
       return NULL;
     }
 #ifdef XML_CONTEXT_BYTES
-    int keep = (int)(bufferPtr - buffer);
-
+    keep = (int)(bufferPtr - buffer);
     if (keep > XML_CONTEXT_BYTES)
       keep = XML_CONTEXT_BYTES;
     neededSize += keep;