[OE-core] gcc default version change (and qt4)

[Richard Purdie]

I'd like to warn people that I'm pretty close to throwing the version
switch to default to gcc 4.7 at the same time as merging in Khem's
patches. I don't think this will surprise anyone, we've talked about
doing it post release for long enough.

It also appears that qt 4.7.4 has issues with gcc 4.7 and 4.8.1 is fixed
so I'm going to change the default version on that at the same time.

Since the tests on the autobuilder are looking pretty good now, I'll
probably do this sooner than later, maybe on Monday.

I'll probably then give it a week, then assuming no reason to change
back to the older version, I'll remove gcc 4.6 and qt 4.7.4 from
OE-Core. They may get added to meta-oe's toolchain layer at that point
but that is up to the appropriate maintainers.

Cheers,

Richard