Abi: Add endianness method

For now this uses the architecture to decide which endianness to use.
That does not work too well, so a endianness field is needed for
the master branch.

Change-Id: I394a959c4182271ee9847de7c8da1788a027c3a2
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
Qbs: Fix crash in QbsRunConfiguration

Change-Id: I975b8b0f9a2c761850d34e1ab26ff343be7a16c7
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>
QtSupport: More helper methods for BaseQtVersion

Add a method to query debug/release build availability and one for
the documentation path.

Qbs wants to know those and I do not want to hardcode QtSupport
details there.

Change-Id: I32c83167270dd34a81c4ab3f65e9d92b8f6bca90
Reviewed-by: Daniel Teske <daniel.teske@digia.com>