Add "-format darwin" to llvm-size to be like darwin's size(1) -m output, and
and the -l option for the long format.  Also when the object is a Mach-O
file and the format is berkeley produce output like darwin’s default size(1)
summary berkeley derived output.

Like System V format, there are also some small changes in how and where
the file names and archive member names are printed for darwin and
Mach-O.

Like the changes to llvm-nm these are the first steps in seeing if it is
possible to make llvm-size produce the same output as darwin's size(1).