Make unicode ranges in font take precedence over codepage

Change 4b2c73b4767bcb512cbc17f65186eac5d004db07 triggered a
regression on Android, because the DroidSansFallback.ttf font
has codepage ranges that list Arabic as a supported codepage
despite the fact that the font has no glyphs for Arabic.

If a font has valid unicode ranges which does not specify
support for e.g. Arabic, then the code page ranges for the
same script should be ignored.

[ChangeLog][Android][Fonts] Fixed support for Arabic text.

Task-number: QTBUG-36789
Change-Id: I7c5a0e303fd9ed2733275814fe752ae0fb54a207
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>
QtConcurrent: Extend workaround GCC bug 58800 in median calculation

GNU/Linux distributions like Fedora update the __GLIBCXX__ date (e.g.
because of applied extra patches on top) and thus make the current
workaround useless. As long as no official gcc/libstdc++ version is
released, we can increment the "upper bound" date to cover such cases.

See also comment #1 at QTCREATORBUG-11129.

Change-Id: I1fdf6f312664163f6a99a8eddf490646ff25a87d
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>