Revert "Make OpenGL texture glyph cache use the right freetype glyphs"

This reverts commit f78661b0.

The reverted patch was working around that QFontEngineFT was using
the poor QFontEngine fall back. That issue was fixed in commit
0b7beaaa

, and the work around
is no longer needed.

This also fixes a rare problem with the workaround when the fontengine
and the glyph-cache do not share the same default glyph format which
can happen with QRawFonts.

Change-Id: I150f70a003b137c1d145f6f70cda568c85633e5c
Reviewed-by: Gunnar Sletta <gunnar.sletta@jollamobile.com>