add PIRegularExpression

3rd/pcre2/testdata/testoutput23

@@ -0,0 +1,11 @@
+# This test is run when PCRE2 has been built with --enable-never-backslash-C,
+# which disables the use of \C. All we can do is check that it gives the 
+# correct error message.
+
+/a\Cb/
+Failed: error 185 at offset 3: using \C is disabled in this PCRE2 library
+
+/a[\C]b/
+Failed: error 107 at offset 3: escape sequence is invalid in character class
+
+# End of testinput23