Only use alloca.h on OSes that have it.

Reported by jontow on IRC in #asterisk-dev


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@43230 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/strcompat.c

@@ -25,9 +25,12 @@
 #include <ctype.h>
 #include <stdio.h>
 #include <stdlib.h>
-#include <alloca.h>
 #include <string.h>
 
+#ifdef HAVE_ALLOCA_H
+#include <alloca.h>
+#endif
+
 #ifndef HAVE_STRSEP
 char *strsep(char **str, const char *delims)
 {