Rebuild libpng and zlib using GCC 4.8.1

Which should resolve those undefined references errors with libpng.
Rebuilt zlib just to be safe.

src/d_main.c

@@ -72,6 +72,7 @@ int	snprintf(char *str, size_t n, const char *fmt, ...);
 #include "keys.h"
 #include "filesrch.h" // refreshdirmenu, mainwadstally
 #include "g_input.h" // tutorial mode control scheming
+#include "png.h"
 
 #ifdef CMAKECONFIG
 #include "config.h"
@@ -964,6 +965,8 @@ void D_SRB2Main(void)
 	"We do not claim ownership of SEGA's intellectual property used\n"
 	"in this program.\n\n");
 
+	CONS_Printf("libpng version: %s\n", png_libpng_ver);
+
 	// keep error messages until the final flush(stderr)
 #if !defined (PC_DOS) && !defined(NOTERMIOS)
 	if (setvbuf(stderr, NULL, _IOFBF, 1000))