Use off_t when we really mean a file offset.

Not all platforms have declared 'unsigned long' to be a 64 bit value,
but we want to support a 64 bit packfile (or close enough anyway)
in the near future as some projects are getting large enough that
their packed size exceeds 4 GiB.

By using off_t, the POSIX type that is declared to mean an offset
within a file, we support whatever maximum file size the underlying
operating system will handle.  For most modern systems this is up
around 2^60 or higher.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

git-compat-util.h

@@ -70,6 +70,10 @@
 #define PATH_MAX 4096
 #endif
 
+#ifndef PRIuMAX
+#define PRIuMAX "llu"
+#endif
+
 #ifdef __GNUC__
 #define NORETURN __attribute__((__noreturn__))
 #else