Use freetype font engine on Windows

Use freetype font engine on Windows

As windows' fontdatabases also uses functionalities from
qbasicunixfontdatabase it was renamed to qbasicfontdatabase. But instead
of iterating over the font directories' files it uses system calls to
obtain the list of fonts and uses registry values to find the according
filenames to add.
The native font engine was still kept. It can be activated by adding
fontengine=native as platformargument.

Change-Id: I7197bed5d18b8a33d4aa97ce91bfa1cd281b80ea
Reviewed-on: http://codereview.qt-project.org/5839
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@nokia.com>
Sanity-Review: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@nokia.com>