Make sure EmulateInstructionARM doesn't have to have "armv4", "armv6", "armv7"...

Make sure EmulateInstructionARM doesn't have to have "armv4", "armv6", "armv7" as the exact architecture name, the arch name can just start with any of these strings. We need to be able to recognize different variants that might come along and not fail to backtrace completely (which happens when we aren't able to find an architecture that matches) when we don't have exact matches.

llvm-svn: 155045