don't filter out ^QMAKE_.*:
- QMAKE_MKSPECS is not printed any more, so needs no filtering
- QMAKE_VERSION can be simply used now, as we are now rather close to the
  real qmake
- QMAKE_SPEC and QMAKE_XSPEC need to be fetched
  - this fixes the default spec resolution

Change-Id: Ifcfa8b5b9e2bbf5d995940e1bb7f55e7d67aed3e
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>