textproc/the_silver_searcher: Add off64_t patch to fix building

The 'off64_t' type is unavailable on DragonFly BSD and thus causes the
building to fail.  Replace it with 'z_off64_t', which is properly
defined in 'zconf.h' and is already included by this file.  So it should
be portable and a reasonable fix.

ports/textproc/the_silver_searcher/dragonfly/patch-src_zfile.c

@@ -0,0 +1,38 @@
+--- src/zfile.c.orig 2023-11-29 22:40:36 UTC
++++ src/zfile.c
+@@ -4,7 +4,7 @@
+ #include <sys/types.h>
+
+ #ifdef __CYGWIN__
+-typedef _off64_t off64_t;
++typedef _off64_t z_off64_t;
+ #endif
+
+ #include <assert.h>
+@@ -331,14 +331,14 @@ zfile_read(void *cookie_, char *buf, siz
+ }
+
+ static int
+-zfile_seek(void *cookie_, off64_t *offset_, int whence) {
++zfile_seek(void *cookie_, z_off64_t *offset_, int whence) {
+ struct zfile *cookie = cookie_;
+- off64_t new_offset = 0, offset = *offset_;
++ z_off64_t new_offset = 0, offset = *offset_;
+
+ if (whence == SEEK_SET) {
+ new_offset = offset;
+ } else if (whence == SEEK_CUR) {
+- new_offset = (off64_t)cookie->logic_offset + offset;
++ new_offset = (z_off64_t)cookie->logic_offset + offset;
+ } else {
+ /* SEEK_END not ok */
+ return -1;
+@@ -348,7 +348,7 @@ zfile_seek(void *cookie_, off64_t *offse
+ return -1;
+
+ /* Backward seeks to anywhere but 0 are not ok */
+- if (new_offset < (off64_t)cookie->logic_offset && new_offset != 0) {
++ if (new_offset < (z_off64_t)cookie->logic_offset && new_offset != 0) {
+ return -1;
+ }
+