<rdar://problem/13695846>

Enabling LLDB to write to variables that are stored in registers
Previously, this would not work since the Value's Context loses the notion of the data being in a register
We now store an "original" context that comes out of DWARF parsing, and use that context's data when attempting a write



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@180803 91177308-0d34-0410-b5e6-96231b3b80d8