As we add more classes with RValue ref qualified methods we will need
the same _compat trick and no-pch support as QString.
This patch moves the extra compiler to precompile_header.prf which is
automatically included when pch is used.
Change-Id: I422a355fd11f499ce0648a90b0385f2a6f699fcb
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
