wince: Build fix, CONST conflicts with Windows macros.

Don't #undef system macros in header files, they propagate quickly
through other headers and make it very difficult to fix these problems.

Change-Id: Id5efdfa69d0eefa8c740b14f839194039bd9752b
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Generate code conversion to double.

Performance improves by about 15% on fact.3.js when Qt is build in
debug mode.

Change-Id: I4a1c868fe211c1e0f9e7d9a5652f7726b37405d1
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>