Use PCRE2_NO_UTF_CHECK for the second and subsequent matches in

pcre2_substitute().

ChangeLog

@@ -233,6 +233,9 @@ misbehave.
 replacement string was happening before the length setting when the replacement
 string was zero-terminated.
 
+68. In pcre2_substitute() in UTF mode, PCRE2_NO_UTF_CHECK can be set for the 
+second and subsequent calls to pcre2_match().
+
 
 Version 10.20 30-June-2015
 --------------------------

src/pcre2_substitute.c

@@ -280,6 +280,10 @@ do
   rc = pcre2_match(code, subject, length, start_offset, options|goptions,
     match_data, mcontext);
     
+#ifdef SUPPORT_UNICODE
+  if (utf) options |= PCRE2_NO_UTF_CHECK;  /* Only need to check once */
+#endif   
+
   /* Any error other than no match returns the error code. No match when not
   doing the special after-empty-match global rematch, or when at the end of the
   subject, breaks the global loop. Otherwise, advance the starting point by one