Fixed an issue that broke expression parsing related to backing up

all register values. There is some junk that was appearing at the end
of the result the 'g' packet (read all register values). This function
was being called in:

bool
GDBRemoteRegisterContext::ReadAllRegisterValues (lldb::DataBufferSP &data_sp)

Then the packet data for the 'G' packet (write all registers) was being 
placed into "data_sp" so the:

bool
GDBRemoteRegisterContext::WriteAllRegisterValues (const lldb::DataBufferSP &data_sp)

could restore it. In attempting to clean up the extra junk at the end of this
packet data, the packet was getting truncated.

llvm-svn: 131468