lldb: gdb remote support always falls back to $qC when no $qProcessInfo.

See thread here:
http://lists.cs.uiuc.edu/pipermail/lldb-dev/2014-May/003992.html

This is meant to address case 3 that I recently broke with an earlier
change to rectify usage of the $qC message for thread ids, specifically:

3. TOT lldb <=> gdbserver (without $qProcessInfo support and not Apple/iOS).

llvm-svn: 208741