Make unicode ranges in font take precedence over codepage

Change 4b2c73b4

 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>