Make lib/pattern.c a stand-alone library

Make lib/pattern.c a stand-alone library

lib/pattern.c not having dependency on fio.h enables it to be
a stand-alone library, which is useful for debugging purpose.
In fact, most of the files under lib/ directory do things this way.

This requires the previous commit.

--
 # cat ./test6.c
 #include <stdio.h>
 #include "lib/pattern.h"
 int main(void) {
         /* just to see if it compiles */
         paste_format_inplace(NULL, 0, NULL, 0, NULL);
         return 0;
 }
 # gcc -Wall -g ./test6.c ./lib/pattern.c ./lib/strntol.c

Signed-off-by: Tomohiro Kusumi <tkusumi@tuxera.com>
Signed-off-by: Jens Axboe <axboe@fb.com>