Add styles/qmacstyle_mac back to the build, modify
qstylefactory to load it on Q_OS_MAC.
Move helper functions from platforms/mac to
qmacstyle_mac.mm. QMacStyle should now be self-
contained and not rely on anything from platforms/mac.
Change-Id: I68fe40bb7f88c01269968bffd9579b7f3b932d4c
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@nokia.com>
Reviewed-by: Morten Johan Sørvig <morten.sorvig@nokia.com>