libwebp-1.3.0

- 12/16/2022: version 1.3.0
  This is a binary compatible release.
  * add libsharpyuv, which exposes -sharp_yuv/config.use_sharp_yuv
    functionality to other libraries; libwebp now depends on this library
  * major updates to the container and lossless bitstream docs (#448, #546,
    #551)
  * miscellaneous warning, bug & build fixes (#576, #583, #584)

1. 7c76255 autoconf: update ax_pthread.m4 by James Zern · 12 years ago
2. 1d40a8b configure: add pthread detection by James Zern · 13 years ago
3. b247a3b Create the m4 directory, and also place .gitignore in there for libtool. by Pascal Massimino · 15 years ago