fix missing ctype.h include

This file uses isspace but doesn't include ctype.h leading to:
isomac.c: In function 'get_null_defines':
isomac.c:305:30: warning: implicit declaration of function 'isspace' [-Wimplicit-function-declaration]
	for (end = start + 1; !isspace (*end) && *end != '\0'; ++end)

1 files changed, 1 insertions, 0 deletions

diff --git a/stdlib/isomac.c b/stdlib/isomac.c
index 816298b..e01fd38 100644
--- a/stdlib/isomac.c
+++ b/stdlib/isomac.c
@@ -70,6 +70,7 @@
 # define _GNU_SOURCE 1
 #endif
 
+#include <ctype.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>