Fix minor initialization bug in Registers_x86_64.
Fix minor initialization bug in Registers_x86_64.

According to kledzik, this constructor isn't live code, so no functionality
change.



git-svn-id: 6a9f6578bdee8d959f0ed58970538b4ab6004734@196550 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/libcxxabi,llvm-mirror/libcxxabi,llvm-mirror/libcxxabi,llvm-mirror/libcxxabi,llvm-mirror/libcxxabi