This commit allows to support the full unicode range in GuiFontMetrics thus fixing...

This commit allows to support the full unicode range in GuiFontMetrics thus fixing the crash in this bug:

http://bugzilla.lyx.org/show_bug.cgi?id=3759

It also simplifies and fix the smallcaps case which was not correct WRT unicode. Even though I don't know if toUpper() means something in the non ucs2 range.

FYI, I used toqstr() to do the ucs4 -> ucs2 conversion when needed. This helper method works only with Qt >= 4.2.

* GuiFontMetrics::smallcapsWidth(): changed to work with single ucs4 characters.
* GuiFontMetrics::xxx(): make sure that font metrics works with characters not in the ucs2 range.

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@18593 a592a061-630c-0410-9148-cb99ea01b6c8