Change the output of llvm-nm and llvm-size for Mach-O universal files (aka
fat files) to print “ (for architecture XYZ)” for fat files with more than
one architecture to be like what the darwin tools do for fat files.

Also clean up the Mach-O printing of archive membernames in llvm-nm to use
the darwin form of "libx.a(foo.o)".


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211316 91177308-0d34-0410-b5e6-96231b3b80d8