Introduces core file support for Linux x86-64 using 'lldb a.out -c core'.
  TODO: Support for RegisterContext_x86_64::ReadFPR.

Patch by Samuel Jacob!


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@186207 91177308-0d34-0410-b5e6-96231b3b80d8