XFA: Upgrade libpng to 1.6.20.

third_party/libpng/0000-build-config.patch

Index: third_party/libpng/0000-build-config.patch
diff --git a/third_party/libpng/0000-build-config.patch b/third_party/libpng/0000-build-config.patch
new file mode 100644
index 0000000000000000000000000000000000000000..4f0013970ab76936caced8950112bcbeeb3d6124
--- /dev/null
+++ b/third_party/libpng/0000-build-config.patch
@@ -0,0 +1,43 @@
+diff a/third_party/libpng/pngmem.c b/third_party/libpng/pngmem.c
+--- a/third_party/libpng/pngmem.c
++++ b/third_party/libpng/pngmem.c
+@@ -19,6 +19,9 @@
+ 
+ #include "pngpriv.h"
+ 
++void*	FXMEM_DefaultAlloc(int byte_size, int);
++void	FXMEM_DefaultFree(void* pointer, int);
++
+ #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
+ /* Free a png_struct */
+ void /* PRIVATE */
+@@ -92,7 +95,7 @@
+ 
+       else
+ #endif
+-         return malloc((size_t)size); /* checked for truncation above */
++         return FXMEM_DefaultAlloc((int)size, 0);
+    }
+ 
+    else
+@@ -249,7 +252,7 @@
+       return;
+ #endif /* USER_MEM */
+ 
+-   free(ptr);
++   FXMEM_DefaultFree(ptr, 0);
+ }
+ 
+ #ifdef PNG_USER_MEM_SUPPORTED
+diff a/third_party/libpng/pngstruct.h b/third_party/libpng/pngstruct.h
+--- a/third_party/libpng/pngstruct.h
++++ b/third_party/libpng/pngstruct.h
+@@ -27,7 +27,7 @@
+    /* We must ensure that zlib uses 'const' in declarations. */
+ #  define ZLIB_CONST
+ #endif
+-#include "zlib.h"
++#include "third_party/zlib_v128/zlib.h"
+ #ifdef const
+    /* zlib.h sometimes #defines const to nothing, undo this. */
+ #  undef const