Added two new test types: @debugserver_test and @llgs_test.

TestLldbGdbServer now supports both lldb-gdbserver (llgs) and
debugserver tests.  Similar to the dsym/dwarf tests, they allow
running the same underlying gdb remote protocol tests against
lldb-gdbserver and debugserver.  This will help make sure the
protocol-level tests for lldb-gdbserver faithfully represent
what debugserver does on OS X.

Switched back gdb remote protocol test logging to warning
and above (accidentally submitted it at debug level in a
recent commit).