Skip useless memset() when copying a bitmap
shaper: add FriBidi error handling

It is unlikely, but FriBidi might not process a string correctly,
and we should handle that. Tested by making it fail always. This
should also fix some compiler warnings.
Merge pull request #102 from grigorig/fribidi-errorhandle

shaper: add FriBidi error handling
Use FT_Outline_EmboldenXY if available
Close gaps in borders of self-intersecting glyphs

If the glyph is self-intersecting, so are the stroke
borders produced by stroking it. Normally, there is an
"inside" and an "outside" stroke border, but they swap
roles around self-intersections, the "inside" one going
on the outside while the "outside" one stays inside.
Currently, we take only the "outside" border, which thus
hides behind the main glyph around self-intersections.

Keep both stroke borders instead.

NOPE: this gives only a thick path around the edges
of the glyph, which breaks blur.
stroke_outline: merge original and stroked outline to fix blur
fix_freetype_stroker: ensure overall clockwise direction

The stroked outline's overall direction is always clockwise, so we
need this to be able to correctly add it to the original outline.
Disable fix_outline for debugging
stroke_outine: output outlines for debugging