Revert last commit, apparently buildbot lied to me.

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@89397 65c4cc65-6c06-0410-ace0-fbb531ad65f3

include/asterisk/compat.h

@@ -52,14 +52,9 @@
 #endif
 
 #ifdef HAVE_ALLOCA_H
-#include <alloca.h>
-#elif defined(__GNUC__)
-#define alloca __builtin_alloca
-#elif defined(_AIX)
-#define alloca __alloca
-#elif defined(_MSC_VER)
-#include <malloc.h>
-#define alloca _alloca
+#include <alloca.h>    /* not necessarily present - could be in stdlib */
+#elif defined(HAVE_ALLOCA)
+#include <malloc.h>    /* see if it is here... */
 #endif
 
 #include <stdio.h>	/* this is always present */