Use ctype.h for isalpha()/isdigit()

Author: zdohnal

cupsconnection.c

@@ -26,6 +26,7 @@
 #ifndef __SVR4
 #include <paths.h>
 #endif
+#include <ctype.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>