Fix symbol fonts support with FT engine

Fix symbol fonts support with FT engine

It appears that the symbol_map we obtained with FreeType doesn't
work for common symbol fonts like Wingdings, in previous X11 code
we use the code path with normal charmap, to enable it we need to
make sure QT_NO_FONTCONFIG is not defined. And since the FcCharset
functions doesn't really operates on the font database, we can
safely skip the mutex calls.

Change-Id: I8c484de200be1d47c053b10be2c51d2273dcd359
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@nokia.com>