travis-ci: upgraded pcre to 8.40.

Author: agentzh

.travis.yml

@@ -34,7 +34,7 @@ env:
     - LUAJIT_LIB=$LUAJIT_PREFIX/lib
     - LUAJIT_INC=$LUAJIT_PREFIX/include/luajit-2.1
     - LUA_INCLUDE_DIR=$LUAJIT_INC
-    - PCRE_VER=8.39
+    - PCRE_VER=8.40
     - PCRE_PREFIX=/opt/pcre
     - PCRE_LIB=$PCRE_PREFIX/lib
     - PCRE_INC=$PCRE_PREFIX/include