Update libpng.py to 1.6.56

ChangeLog.md

@@ -36,6 +36,7 @@ See docs/process.md for more on how version tagging works.
   emscripten.  If you still need to support extremely old browsers, you can
   manually transpile the output of emscripten (e.g. using babel for JS and
   binaryen for wasm). (#26677)
+- libpng port updated from 1.6.55 to 1.6.56. (#26592)
 - The `-m64` compiler flag is now honored, and works as an alias for
   `-sMEMORY64` and/or `--target=wasm64`. (#26765)
 - The autopersistence feature in IDBFS mount now supports registering a global

test/third_party/libpng/pngtest.c

@@ -2028,4 +2028,4 @@ main(void)
 #endif
 
 /* Generate a compiler error if there is an old png.h in the search path. */
-typedef png_libpng_version_1_6_55 Your_png_h_is_not_version_1_6_55;
+typedef png_libpng_version_1_6_56 Your_png_h_is_not_version_1_6_56;

tools/ports/libpng.py

@@ -6,8 +6,8 @@
 import os
 import shutil
 
-TAG = '1.6.55'
-HASH = '45d3c4c3bd3d22dd93026e1bdff8df8133459a2903fb70be178899a55d256bab55bb5c4220d790202fce578e346c040c5c00e1f004cf5c4dcbf387a30d43e701'
+TAG = '1.6.56'
+HASH = 'e9b7c90e5b29d877e0c0888fe35e5498ae513619943728d7a05269b261786c476808df06de460ec27f6d045cf7193a5e3656b95c553539b4edcdd2fd0c5fa422'
 
 deps = ['zlib']
 variants = {