Fixed all overlapping prompt issues.

I carefully reviewed exactly how the IOHandlers interact and found places where we weren't properly controlling things. There should be no overlapping prompts and all output should now come out in a controlled fashion.

<rdar://problem/16111293>



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@202525 91177308-0d34-0410-b5e6-96231b3b80d8