Compile without RTTI support

We need to be able to compile without RTTI support. Fortunately
QPaintEngine has built-in type info. No RTTI support is the
default configuration on Windows with MSVC2010, so this is
required to fix the build there.

Change-Id: I89b1ed4879fd0e8e0d61ef12d77f6961fd0b07e5
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Yunqiao Yin <charles.yin@nokia.com>