Sculpt: fix windows compile issues, pointed out by JMS, thanks!

source/blender/blenlib/intern/string.c

@@ -42,6 +42,9 @@
 
 #include "BLI_dynstr.h"
 #include "BLI_string.h"
+#ifdef WIN32
+#include "BLI_winstuff.h"
+#endif
 
 char *BLI_strdupn(const char *str, int len) {
 	char *n= MEM_mallocN(len+1, "strdup");

source/blender/gpu/intern/gpu_buffers.c

@@ -31,6 +31,7 @@
  */
 
 #include <limits.h>
+#include <stddef.h>
 #include <string.h>
 
 #include "GL/glew.h"