Add Debugger::InitializeForLLGS to allow ref counted LLGS initialization.

After http://reviews.llvm.org/D8133 landed as r231550 process launch on remote platform stopped working.

This adds Debugger::InitializeForLLGS and tracks whether one or both of Initialize and InitializeForLLGS have been called, calling only the corresponding lldb_private::Terminate* methods as necessary. Since lldb_private::Terminate calls lldb_private::TerminateForLLGS, the latter method may be called twice if Initialize was called for both however the terminate methods ensure they are only called once after being initialized.

This still maintains the reduced binary size, though it does now technically link in lldb_private::Terminate on lldb-server even though this should never be called.

This should resolve the issue raised in http://reviews.llvm.org/D8133 where Debugger::Terminate assumed that there were 0 references to debugger and terminated early.

Differential Revision: http://reviews.llvm.org/D8183

llvm-svn: 231808