Update ABISysV_arm64::RegisterIsVolatile to accept registers prefixed with r
Update ABISysV_arm64::RegisterIsVolatile to accept registers prefixed with r

Summary:
While the specification says that the 64bit registers are prefixed with
`x`, it seems that many people still use `r`. Until recently, we had been using
the `r` prefix instead of the `x` prefix in ds2. This caused lldb to fail during
unwinding. I think it's reasonable to check for a register prefixed with `r`,
since some people still choose to use `r`.

Reviewers: sas, fjricci, clayborg

Reviewed By: sas, clayborg

Subscribers: aemerson, javed.absar, kristof.beyls

Differential Revision: https://reviews.llvm.org/D38376

Change by Alex Langford <apl@fb.com>

git-svn-id: 4c4cc70b1ef44ba2b7963015e681894188cea27e@315221 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,llvm-mirror/lldb,apple/swift-lldb,llvm-mirror/lldb,llvm-mirror/lldb,apple/swift-lldb,llvm-mirror/lldb,llvm-mirror/lldb