Move c/h files implementing/defining standard library stuff into a new libc directory, also standard'ify some parts of the code base (almost entirely #include fixes).

This is to a) to cleanup firmware/common and firmware/include a bit, but also b) for Rockbox as an application which should use the host system's c library and headers, separating makes it easy to exclude our files from the build.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@25850 a1c6a512-1295-4272-9138-f99709370657

apps/tree.c

@@ -19,9 +19,9 @@
  *
  ****************************************************************************/
 #include <stdio.h>
-#include <string.h>
 #include <stdlib.h>
 #include <stdbool.h>
+#include "string-extra.h"
 
 #include "applimits.h"
 #include "dir.h"
@@ -32,7 +32,6 @@
 #include "kernel.h"
 #include "usb.h"
 #include "tree.h"
-#include "sprintf.h"
 #include "audio.h"
 #include "playlist.h"
 #include "menu.h"