Doc: Solved link and autolink errs qnamespace.qdoc

Task-number: QTBUG-40362
Change-Id: I81166dc3a54427e2d2d81f640162f6c338947849
Reviewed-by: Martin Smith <martin.smith@digia.com>
Fix hb_face leaking in QFontEngineFT

Since HarfBuzz-old's HB_Face doesn't support ref-counting,
it is impossible to keep the same behavior as for NG's ref-counted hb_face
when we're going to reparent the data of unknown type in QFontEngineFT.

We should either not release the object returned by harfbuzzFace(),
or introduce ref-counting for HB-old's HB_Face. Stop referencing HB-NG's
objects on access for now and thus avoid a need to release them manually.

Task-number: QTBUG-42674
Change-Id: Ia21e7ba9c17185796b0dd98c2c27d02566f2a701
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@theqtcompany.com>