by splicing function bodies from the src module to the destination module.
This speeds up linking quite a bit, e.g. gccld time on 176.gcc from 26s -> 20s
when forming the .rbc file, with a profile build. One of the really strange
but cool effects of this patch is that it speeds up the optimizers as well,
from 12s -> 10.7s, presumably because of better locality???
In any case, this is just a first step. We can trivially get rid of the
LocalMap now and do other simplifications.
llvm-svn: 17893
