check for isblank() at configuration stage. If not available

provide a suitable replacement for use in our ISBLANK macro

configure.ac

@@ -553,6 +553,7 @@ AC_CHECK_MEMBER(struct addrinfo.ai_flags,
 
 
 AC_CHECK_FUNCS( bitncmp \
+                isblank \
                 if_indextoname,
 dnl if found
 [],

setup_once.h

@@ -115,7 +115,6 @@
  */
 
 #define ISSPACE(x)  (isspace((int)  ((unsigned char)x)))
-#define ISBLANK(x)  (isblank((int)  ((unsigned char)x)))
 #define ISDIGIT(x)  (isdigit((int)  ((unsigned char)x)))
 #define ISALNUM(x)  (isalnum((int)  ((unsigned char)x)))
 #define ISXDIGIT(x) (isxdigit((int) ((unsigned char)x)))
@@ -125,6 +124,13 @@
 #define ISUPPER(x)  (isupper((int)  ((unsigned char)x)))
 #define ISLOWER(x)  (islower((int)  ((unsigned char)x)))
 
+#ifdef HAVE_ISBLANK
+#define ISBLANK(x)  (isblank((int)  ((unsigned char)x)))
+#else
+#define ISBLANK(x)  (int)((((unsigned char)x) == ' ') || \
+                          (((unsigned char)x) == '\t'))
+#endif
+
 
 /*
  * Typedef to 'int' if sig_atomic_t is not an available 'typedefed' type.