[libpng15] Imported from libpng-1.5.18beta02.tar
[libpng15] Bump version to 1.5.18beta03
[libpng15] Fix typo in CHANGES and ANNOUNCE
[libpng15] Removed configure-generated "compile" file.
[libpng15] Fix typo in pngrtran.c
[libpng15] Re-added "compile" (libpng15 branch includes configure-generated

stuff).