- updated to 1.5.7 (latest stable release)

- updated to 1.5.7 (latest stable release)
  note: new soname; libpng left on LIBPNG_1_4 branch (as default libpng) or in libpng14.spec (as non-default)
- updated pngminus patch
- apng patch updated from libpng-apng project
- added apng-fix patch to avoid make check failure

Changed files:
    libpng-apng-fix.patch -> 1.1
    libpng-apng.patch -> 1.14
    libpng-pngminus.patch -> 1.8
    libpng.spec -> 1.190