Fix broken drawing with large fonts using QStaticText and FreeType

Fix broken drawing with large fonts using QStaticText and FreeType

In FreeType, there's a fall back to QFontEngine::alphaMapForGlyph()
when the fonts are very large. Since this uses a QPainterPath containing
an unhinted glyph, the use of hinted metrics would sometimes lead to
the glyphs being clipped because they would be positioned slightly
outside the image they were painted into. When outline drawing is on,
it makes sense to return unhinted metrics, since the glyphs we will
actually use are unhinted.

Task-number: QTBUG-19067
Reviewed-by: Jiang Jiang