Essentially move the glyph mapping to normalization process.
The effect on Devanagari is small (but observable).  Should be more
observable in simple text, like ASCII.

Preparing for merging map_glyphs() and normalize().

To room for more allocations, coming.

This reverts commit 30ec9002.

See previous commit.

This reverts commit 0981068b.

I was confused.  Even if we access coverage[0] unconditionally, we don't
need bound checks since the array machinary already handles that.

And misc linking fixes.

Apparently even that doesn't make check-internal-symbols.sh happy with
mingw32.  Going to disable that for DLLs again, but hopefully the
export-file is doing *something*.

https://bugs.freedesktop.org/show_bug.cgi?id=53233

Implemented for Arabic, Hebrew, and generic marks.
Activated if no GPOS table present.

Used when there is no GPOS.

Fixes logic also, where before we were always matching if glyphs_len==1
and a ligature started with the glyph.

'rclt' is "Required Contextual Forms" being proposed by Microsoft.
It's like 'calt', but supposedly always on.  We apply 'calt' anyway,
and now apply this too.

Lifted from https://bugzilla.mozilla.org/show_bug.cgi?id=728866

...again.

Patch from Martin Hosken.

We already set recount to INVALID when destroying.
This block was not necessary.