Change to prevent the failure of "make distclean" on the missing...

Change to prevent the failure of "make distclean" on the missing 'regex/Makefile' (and, later, 'strings/Makefile').


configure.in:
  The subdirectories 'strings' and 'regex' were each contained in both the 'sql_client_dirs' and the 'sql_server_dirs' macro.
  As these are used to form the (Makefile) macro 'SUBDIRS' and 'DIST_SUBDIRS', these subdirectories will get listed there twice.
  This causes a failure of the (recursive) "make distclean", so this double inclusion must be prevented.

configure.in

@@ -2830,7 +2830,7 @@ thread_dirs=
 
 dnl This probably should be cleaned up more - for now the threaded
 dnl client is just using plain-old libs.
-sql_client_dirs="libmysql strings regex client"
+sql_client_dirs="libmysql client"
 linked_client_targets="linked_libmysql_sources"
 CLIENT_LIBS=$NON_THREADED_CLIENT_LIBS
 if test "$THREAD_SAFE_CLIENT" != "no"