isdigit(), isspace(), etc are likely to give surprising results if passed a
signed char.  We should always cast the argument to unsigned char to avoid
that.  Error in commit 
d78a7d9c7fa3e9cd, found by buildfarm member gaur.
 
                                                                         errmsg("non-ASCII affix flag \"%s\"",
                                                                                        sflag)));
                                                }
-                                               else if (isdigit(*next))
+                                               else if (isdigit((unsigned char) *next))
                                                {
                                                        if (!met_comma)
                                                                ereport(ERROR,
                                                                                                sflag)));
                                                        met_comma = true;
                                                }
-                                               else if (!isspace(*next))
+                                               else if (!isspace((unsigned char) *next))
                                                {
                                                        ereport(ERROR,
                                                                        (errcode(ERRCODE_CONFIG_FILE_ERROR),