Rewrite how the indirect call bonus is handled. This now works by:

a) Making it a per call site bonus for functions that we can move from
indirect to direct calls.
b) Reduces the bonus from 500 to 100 per call site.
c) Subtracts the size of the possible newly inlineable call from the
bonus to only add a bonus if we can inline a small function to devirtualize
it.

Also changes the bonus from a positive that's subtracted to a negative
that's added.

Fixes the remainder of rdar://8546196 by reducing the object file size
after inlining by 84%.

llvm-svn: 124916