Disable frame pointer elimination when using -pg

This diff makes sure that the driver does not pass
-fomit-frame-pointer or -momit-leaf-frame-pointer to
the frontend when -pg is used. Currently, clang gives 
an error if -fomit-frame-pointer is used in combination 
with -pg, but -momit-leaf-frame-pointer was forgotten.
Also, disable frame pointer elimination in the frontend 
when -pg is set.

Patch by Stefan Kempf.

llvm-svn: 253846