introduce SH 2a support

[Alexandre Oliva]

> What happens when you configure for little endian default and use -m2a ?

Same as when you configure for little endian default and use -m1, I
suppose.  It's probably just as broken.

> I think you intended just to change the definition.

Rats, I thought I'd caught all of these :-(

I'll ask people that are still working on SH2a to look into this.
Thanks for the careful review, and sorry that I didn't catch them all
myself.

-- 
Alexandre Oliva             http://www.ic.unicamp.br/~oliva/
Red Hat Compiler Engineer   aoliva@{redhat.com, gcc.gnu.org}
Free Software Evangelist  oliva@{lsd.ic.unicamp.br, gnu.org}