zlib: split up to match original source tree

While looking to upgrade to zlib-1.2.5, the current mondo merge of
multiple files into a single was making things way more difficult
than it should have been.  Hard to pick out what has been changed
to port it to U-Boot, been removed as useless, and bug fixes added
after the fact.

So split the single file up into the original file names, and merge
non-essential changes back from the original tree (for some reason,
style in code in a bunch of places was changed to U-Boot style even
though this isn't "U-Boot" code).

The original build style is retained -- we have a single zlib.c that
includes all the other files, and that is the only file we compile.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

lib/zlib/zlib.c

@@ -0,0 +1,24 @@
+/*
+ * This file is derived from various .h and .c files from the zlib-1.2.3
+ * distribution by Jean-loup Gailly and Mark Adler, with some additions
+ * by Paul Mackerras to aid in implementing Deflate compression and
+ * decompression for PPP packets.  See zlib.h for conditions of
+ * distribution and use.
+ *
+ * Changes that have been made include:
+ * - changed functions not used outside this file to "local"
+ * - added minCompression parameter to deflateInit2
+ * - added Z_PACKET_FLUSH (see zlib.h for details)
+ * - added inflateIncomp
+ */
+
+#include "zutil.h"
+#include "inftrees.h"
+#include "inflate.h"
+#include "inffast.h"
+#include "inffixed.h"
+#include "inffast.c"
+#include "inftrees.c"
+#include "inflate.c"
+#include "zutil.c"
+#include "adler32.c"