clean up CPP includes

Try to only include headers which are really needed.  We should
particularly check all "headers including other headers".  The
long-term goal is to have a manageable, small API for plugins
(decoders, output) without so many mpd internals cluttering the
namespace.

git-svn-id: https://svn.musicpd.org/mpd/trunk@7319 09075e82-0dd4-0310-85a5-a0d7c8717e4f

src/sig_handlers.c

@@ -18,8 +18,6 @@
  */
 
 #include "sig_handlers.h"
-#include "player.h"
-#include "playerData.h"
 #include "playlist.h"
 #include "directory.h"
 #include "command.h"
@@ -27,7 +25,6 @@
 #include "log.h"
 #include "player.h"
 #include "decode.h"
-#include "os_compat.h"
 
 int handlePendingSignals(void)
 {