This patch moves the forward declarations of command-line cl::* externs in MachODump.cpp and llvm-objdump.cpp into the headers corresponding to the file that defines the variable. At the same time, these externs are moved into the llvm::objdump namespace. The externs that are not referenced outside their defining translation unit are made static.
This does not factor out uses of the Mach-O options from llvm-objdump.cpp.