For glyphs with OVERLAP_SIMPLE or OVERLAP_COMPOUND, set
FT_OUTLINE_OVERLAP to render them with direct oversampling, which
mitigates artifacts (see 3bb512bc9f).
* include/freetype/ftimage.h (FT_OUTLINE_OVERLAP): Redefine to rhyme
with OVERLAP_SIMPLE.
* src/base/ftgloadr.c (FT_GlyphLoader_Rewind): Reset outline flags.
* src/truetype/ttgload.c
(TT_Load_Simple_Glyph): Retain OVERLAP_SIMPLE.
(load_truetype_glyph): Retain OVERLAP_COMPOUND.
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