Update UPGRADING wrt. PCRE2

The upgrade to PCRE2 should mostly be transparent to existing code, but
apparently there are some minor differences, which warrant a note in
UPGRADING (and consequently, in the migration guide).

diff --git a/UPGRADING b/UPGRADING
index 2607cc291856b0415409e7b1bc190e006633a4cc..adc813349d2ee4ef7e195d9c7c317add367390ea 100644 (file)
--- a/UPGRADING
+++ b/UPGRADING
@@ -329,6 +329,11 @@ JSON:
   . Support for ODBCRouter has been removed.
   . Support for Birdstep has been removed.
 
+PCRE:
+  . The PCRE extension has been upgraded to PCRE2, which may cause minor
+    behavioral changes, and augments the existing regular expression syntax.
+    See <https://wiki.php.net/rfc/pcre2-migration> for details.
+
  ZIP:
   . Bundled libzip has been dropped,
     system library is now required.