Feedback from Jim: Change the "optimized code" warning to be entirely

contained within Process so that we won't be duplicating the warning
message if other parts of the code want to issue the message.  Change
Process::PrintWarning to be a protected method - the public method
will be the PrintWarningOptimization et al.  Also, Have
Thread::FunctionOptimizationWarning shortcut out if the warnings
have been disabled so that we don't (potentially) compute parts of
the SymbolContext unnecessarily.

llvm-svn: 244436