Windows: Fix ntohl() related warnings about printf formatting

On Windows, ntohl() returns unsigned long.  On Unix it returns
uint32_t.  This makes choosing a suitable printf format string
hard.

This commit introduces a mingw specific helper function
git_ntohl() that casts to unsigned int before returning.  This
makes gcc's printf format check happy.  It should be safe because
we expect ntohl to use 32-bit numbers.

Signed-off-by: Steffen Prohaska <prohaska@zib.de>
Signed-off-by: Johannes Sixt <johannes.sixt@telecom.at>

compat/mingw.h

@@ -186,6 +186,10 @@ pid_t mingw_spawnvpe(const char *cmd, const char **argv, char **env);
 void mingw_execvp(const char *cmd, char *const *argv);
 #define execvp mingw_execvp
 
+static inline unsigned int git_ntohl(unsigned int x)
+{ return (unsigned int)ntohl(x); }
+#define ntohl git_ntohl
+
 sig_handler_t mingw_signal(int sig, sig_handler_t handler);
 #define signal mingw_signal