simplify inclusion of system header files.

This is a mechanical clean-up of the way *.c files include
system header files.

 (1) sources under compat/, platform sha-1 implementations, and
     xdelta code are exempt from the following rules;

 (2) the first #include must be "git-compat-util.h" or one of
     our own header file that includes it first (e.g. config.h,
     builtin.h, pkt-line.h);

 (3) system headers that are included in "git-compat-util.h"
     need not be included in individual C source files.

 (4) "git-compat-util.h" does not have to include subsystem
     specific header files (e.g. expat.h).

Signed-off-by: Junio C Hamano <junkio@cox.net>

daemon.c

@@ -1,20 +1,10 @@
-#include <signal.h>
-#include <sys/wait.h>
-#include <sys/socket.h>
-#include <sys/time.h>
-#include <sys/poll.h>
-#include <netdb.h>
-#include <netinet/in.h>
-#include <arpa/inet.h>
-#include <syslog.h>
-#include <pwd.h>
-#include <grp.h>
-#include <limits.h>
-#include "pkt-line.h"
 #include "cache.h"
+#include "pkt-line.h"
 #include "exec_cmd.h"
 #include "interpolate.h"
 
+#include <syslog.h>
+
 #ifndef HOST_NAME_MAX
 #define HOST_NAME_MAX 256
 #endif