- portability fix for AIX in include/my_sys.h: define alloca as a

   compiler builtin when using gcc


include/my_sys.h:
   - Portability fix: define alloca as a compiler builtin on systems
     that have gcc but no alloca.h (e.g. some IBM AIX flavors), use
     "#pragma alloca" when using IBMs compiler (xlr_C)

include/my_sys.h

@@ -146,6 +146,15 @@ extern my_string my_strdup(const char *from,myf MyFlags);
 #define ORIG_CALLER_INFO    /* nothing */
 #endif
 #ifdef HAVE_ALLOCA
+#ifdef  __GNUC__
+/* Remove any previous definitions.  */
+#undef  alloca
+#define alloca(size)   __builtin_alloca (size)
+#else /* xlc */
+#ifdef _AIX
+ #pragma alloca
+#endif /* _AIX */
+#endif /* __GNUC__  */
 #define my_alloca(SZ) alloca((size_t) (SZ))
 #define my_afree(PTR) {}
 #else