virkeyfile: define IS_ASCII instead c_isascii from gnulib

GLib doesn't provide alternative to c_isascii and this is the only usage
of that macro so define a replacement ourselves.
Signed-off-by: NPavel Hrdina <phrdina@redhat.com>
Reviewed-by: NCole Robinson <crobinso@redhat.com>

src/util/virkeyfile.c

@@ -78,6 +78,7 @@ struct _virKeyFileParserCtxt {
 #define IS_EOF (ctxt->cur >= ctxt->end)
 #define IS_EOL(c) (((c) == '\n') || ((c) == '\r'))
 #define IS_BLANK(c) (((c) == ' ') || ((c) == '\t'))
+#define IS_ASCII(c) ((c) < 128)
 #define CUR (*ctxt->cur)
 #define NEXT if (!IS_EOF) ctxt->cur++;
 
@@ -110,7 +111,7 @@ static int virKeyFileParseGroup(virKeyFileParserCtxtPtr ctxt)
     VIR_FREE(ctxt->groupname);
 
     name = ctxt->cur;
-    while (!IS_EOF && c_isascii(CUR) && CUR != ']')
+    while (!IS_EOF && IS_ASCII(CUR) && CUR != ']')
         ctxt->cur++;
     if (CUR != ']') {
         virKeyFileError(ctxt, VIR_ERR_CONF_SYNTAX, "cannot find end of group name, expected ']'");