At long last, switch us to using GCC 4.4 as the default compiler.

At long last, switch us to using GCC 4.4 as the default compiler.

[I've put some notes into UPGRADING which I quote here.]

That means that any settings that set CCVER to 'gcc44' are not needed
anymore. Instead, CCVER can be set to 'gcc41' to go back to using
GCC 4.1.

The NO_GCC44 options has been removed and will not affect the build
anymore. There is now a NO_GCC41 option that will prevent GCC 4.1 from
building in a similar fashion.

Also, we recommend to do a full buildworld/buildkernel for upgrading.

Thanks-to: sephe, Max Herrgard and everybody else who helped with
           testing and fixing.