* qatar/master:
drawtext: add documentation for the shadow parameters
drawtext: add shadow support.
drawtext: factor draw_glyphs.
drawtext: fix and optimize yuv blend.
drawtext: get rid of divisions in the inner loop.
drawtext: simplify chroma blend and fix chroma alpha.
lavfi: Port drawtext filter by Hemanth from the libavfilter soc repo
Conflicts:
configure
libavfilter/avfilter.h
libavfilter/vf_drawtext.c
Merged-by: Michael Niedermayer <michaelni@gmx.at>