<rdar://problem/15172417>

Added two new GDB server packets to debugserver: "QSaveRegisterState" and "QRestoreRegiterState".

"QSaveRegisterState" makes the remote GDB server save all register values and it returns a save identifier as an unsigned integer. This packet can be used prior to running expressions to save all registers.

All registers can them we later restored with "QRestoreRegiterState:SAVEID" what SAVEID is the integer identifier that was returned from the call to QSaveRegisterState.

Cleaned up redundant code in lldb_private::Thread, lldb_private::ThreadPlanCallFunction.
Moved the lldb_private::Thread::RegisterCheckpoint into its own header file and it is now in the lldb_private namespace. Trimmed down the RegisterCheckpoint class to omit stuff that wasn't used (the stack ID).

Added a few new virtual methods to lldb_private::RegisterContext that allow subclasses to efficiently save/restore register states and changed the RegisterContextGDBRemote to take advantage of these new calls.



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@194621 91177308-0d34-0410-b5e6-96231b3b80d8
<rdar://problem/14814689>

Add a log message to the console that will display the error code when we fail to reply to a mach message.



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@194623 91177308-0d34-0410-b5e6-96231b3b80d8
Added documentation or the new QSaveRegisterState and QRestoreRegisterState packets.



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@194631 91177308-0d34-0410-b5e6-96231b3b80d8