GAS .fpu directive

[Matthew Fortune]

> Same could be said for pre-r6 mips
> code and mipsr6 mips code.  Forcing them to be separate files seems
> harsh.

Thanks to someone in MIPS history, the MIPS assembler pretty much only
modifies an object's attributes based on command line options (and
now a new directive called .module). As such MIPS isn't faced with the
same issue here as it is possible to switch ISAs and operating modes
throughout assembly without impacting the overall object flags.

It's a shame that all the assemblers in binutils are so different
as sharing this kind of feature would give a consistent feel for those
who code for multiple architectures.

Matthew