Fixed detection of 'p' packet support in debugserver,
by appending the thread ID to the test packet when
debugserver requires it.

This allows register writing (and, by extension,
expressions) to work on Mac OS X.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@190007 91177308-0d34-0410-b5e6-96231b3b80d8