Next set of additional error checks for invalid Mach-O files for bad load commands

that use the Mach::dylib_command type for the load commands that are
currently used in the MachOObjectFile constructor.

This contains the missing checks for LC_ID_DYLIB, LC_ID_DYLIB, etc.
load commands and the fields for the Mach::dylib_command type.

Also checks that only an MH_DYLIB or MH_STUB_DYLIB has an
LC_ID_DYLIB load command (and others filetype don’t) and there
is not more than one of these load commands.

llvm-svn: 282008