Stop leaking register infos in the disassemblers.
ARMAsmParser: Plug a leak.

Using an object to do the cleanup may look like overkill, but it's safer and nicer than putting deletes everywhere.
llvm-rtdyld: Don't leak memory managers.

Dyld never outlives MemMgr, just put both on the stack.
MachObjectFile: Don't leak on error.