msvctoolchain: x64 and amd64 are the same

- show cross and native in gui
- add missing compilers

Change-Id: Id48579d4e5dae3a68ed92c0cd2f41309e4f96753
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Peter Kümmel <syntheticpp@gmx.net>