<rdar://problem/13764135>

The "lldb" driver was interfering with STDOUT and STDERR if the output was over 1024 charcters long. The output was grabbing 1024 characters at a time, before it output the characters, it was writing characters to the screen to clear the current line. This has been fixed.

I also fixed the command interpreter from mixing the "(lldb) " prompt in with program output by always manually checking for program output. This was done by having the command interpreter know when it is in the middle of executing a command by setting a bool. This was needed since sometimes when a command would run the target, like with a command like 'expression (int)printf("hello\n")', the process would push a new input reader, and then pop it when it was done. This popping of the input reader would cause the command interpreter to get sent a reactivated message (from the private process state thread) and cause it to ask for another command, even though we were still in the middle of the command ('expression (int)printf("hello\n")'). Now we set a bool to true, run the command and set the bool to false. If we get reactivated while we are in the middle of a command, we don't say we are ready for a new command. This coupled with emitting the STDOUT/STDERR first after each command, followed by the command results, followed by then saying we are ready for a new command, should help cleanup the command line output on all platforms.