move struct pathspec and related functions to pathspec.[ch]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/ls-files.c

@@ -13,6 +13,7 @@
 #include "parse-options.h"
 #include "resolve-undo.h"
 #include "string-list.h"
+#include "pathspec.h"
 
 static int abbrev;
 static int show_deleted;