For llvm-nm and Mach-O files also use function starts info in some

For llvm-nm and Mach-O files also use function starts info in some
cases when printing symbols.  As an improvement to:

r305733 - Change llvm-nm for Mach-O files to use dyld info in some cases when printing symbols

it could be made a bit better if it also read the function starts and faked
up nlist entries to those address not already faked up by the other
dyld info.  This would help with stripped static functions.

rdar://38761029

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@328274 91177308-0d34-0410-b5e6-96231b3b80d8