Fix for libpng undefined symbol

[Thomas Fitzsimmons]

Hi,

With the update to b18 the build was failing on my x86_64 machine with 
an undefined symbol, png_mmx_support, in libpng.

The problem was exposed by the fix for:

http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6577886

specifically this line:

+LDFLAGS_DEFS_OPTION  = -z defs

which causes the linker to disallow undefined symbols.

The failure will happen on systems that support MMX:

$ echo | cpp -dM | grep __MMX__
#define __MMX__ 1

That macro indirectly causes the default png_mmx_support definition to 
be ifdef'd out.

For now I've applied this workaround:

--- openjdk.orig/j2se/make/sun/splashscreen/Makefile    2007-08-19 
15:04:21.000000000 -0400
+++ openjdk/j2se/make/sun/splashscreen/Makefile 2007-08-19 
15:08:45.000000000 -0400
@@ -59,7 +59,7 @@
  # C Flags
  #

-CFLAGS += -DSPLASHSCREEN
+CFLAGS += -DSPLASHSCREEN -DPNG_NO_MMX_CODE

  ifneq ($(PLATFORM), windows)
    CFLAGS += -DWITH_X11

to disable libpng's MMX-specific functions (optimized C implementations 
are used instead).

A better solution would be to conditionally compile pnggccrd.c, which 
defines png_mmx_support, when __MMX__ is defined.  pnggccrd.c would have 
to be patched to fix png_squelch_warnings compile errors.

Tom