Updated the bundled libpng to v1.5.1 (released Feb 3, 2011).

git-svn-id: file:///fltk/svn/fltk/branches/branch-1.3@8523 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

png/TODO

@@ -1,12 +1,11 @@
+/*
 TODO - list of things to do for libpng:
 
 Final bug fixes.
-Improve API by hiding the png_struct and png_info structs.
-Finish work on the no-floating-point version (including gamma compensation)
 Better C++ wrapper/full C++ implementation?
 Fix problem with C++ and EXTERN "C".
 cHRM transformation.
-Improve setjmp/longjmp usage or remove it in favor of returning error codes.
+Remove setjmp/longjmp usage in favor of returning error codes.
 Add "grayscale->palette" transformation and "palette->grayscale" detection.
 Improved dithering.
 Multi-lingual error and warning message support.
@@ -17,9 +16,12 @@ Better filter selection
    (counting huffman bits/precompression?  filter inertia?  filter costs?).
 Histogram creation.
 Text conversion between different code pages (Latin-1 -> Mac and DOS).
-Should we always malloc 2^bit_depth PLTE/tRNS/hIST entries for safety?
-Build gamma tables using fixed point (and do away with floating point entirely).
+Avoid building gamma tables whenever possible.
 Use greater precision when changing to linear gamma for compositing against
   background and doing rgb-to-gray transformation.
 Investigate pre-incremented loop counters and other loop constructions.
 Add interpolated method of handling interlacing.
+Switch to the simpler zlib (zlib/libpng) license if legally possible.
+Extend pngvalid.c to validate more of the libpng transformations.
+
+*/