RFC: set vector changes

[Gedare Bloom]

Hi,

In view of discussion [1] on generalizing set vector across the simple
vectored architectures I have pushed a branch that unifies a lot of
the set vector code. Please review this code.
http://git.rtems.org/gedare/rtems.git/commit/?h=setvec

It touches many BSPs most of which I cannot test and don't have time
to deal with compiling. I compiled one BSP from each target just to
get by. We need a better way to test :)

-Gedare

[1] http://www.rtems.org/pipermail/rtems-devel/2012-March/000493.html