timet64 ABI change for ports architectures

[Matthias Klose]

We'll hard-code the -D_TIME_BITS=64 setting in GCC on all 32bit release 
architectures except for i386 (that is only armhf), and for all other 
ports architectures by default.  If you don't want that change for the 
port, please tell it now (until Friday, Feb 23).

That would include the architectures
armhf
armel
hppa
m68k
powerpc
sh4

For the powerpc multilib m64, I'll make sure to not emit that flag by 
default. The other architectures are no multilib architectures.

Matthias