Store styleName in font database

Store styleName in font database

So that queries like QFontDatabase::styles() can return exactly
the same styles as the system does. Then application can use
QFont::setStyleName() to select those styles later. With a lot
of fonts not providing correct numeric weight/width values and
even if they did, values are usually not directly mapped to
QFont enums, styleName is probably the only reliable way to
select any possible font in the system.

Reviewed-by: QTBUG-13518
Change-Id: Id8a9469b804f1b5bb81d8c7378e7e8778f9a4fff
Reviewed-on: http://codereview.qt.nokia.com/739
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@nokia.com>