A filter parameter fix and a new filter, the regex filter.

The regexfilter is an example of a query rewriting filter that uses
regular expressions to match the SQL text and allows a replacement text
to be used for each match of the regular expression.

Regexfilter has no special SQL undertanding, it merely uses the features
avialable inthe regex library to perform matches.

Statements that span multiple packets are not supported by the regex
filter.

server/include/modutil.h

@@ -33,4 +33,5 @@
 
 extern int	modutil_is_SQL(GWBUF *);
 extern int	modutil_extract_SQL(GWBUF *, char **, int *);
+extern GWBUF	*modutil_repalce_SQL(GWBUF *, char *);
 #endif