Add a test sequence for test_expr_commands_can_handle_quotes(self):

        # runCmd: command alias print_hi expression printf ("\n\tHi!")
        # output: 
        self.runCmd('command alias print_hi expression printf ("\\n\\tHi!")')
        # This fails currently.
        self.runCmd('print_hi')

and modify existing test sequences to escape the escape character '\ to prevent it
from being interpreted by Python before passing on to the lldb command interpreter.

llvm-svn: 121183