Update Skia to r8495
Bug 848491 - Re-apply Bug 795549 - Move TileProc functions into their own file to ensure they only exist once in a library
Bug 848491 - Update DrawTarget and gfxPlatform to use the new Skia APIs
Bug 848491 - Update skia-npapi to use new Skia APIs
Bug 736276 - Add a new SkFontHost that takes a cairo_scaled_font_t
Bug 848491 - Re-apply Bug 777614 - Add our SkUserConfig.h
Bug 848491 - Re-apply bug 687188 - Expand the gradient cache by 2 to store 0/1 colour stop values for clamping.
Bug 848491 - Re-apply 759683 - Handle compilers that don't support SSSE3 intrinsics
Bug 848491 - Re-apply bug 751418 - Add our own GrUserConfig
Bug 848491 - Re-apply bug 817356 - Patch Skia to recognize uppercase PPC/PPC64.
Enable Skia/GPU by default
Bug 874682 - Ensure SkThread_pthreads is built on platforms which use pthreads r=bjacob