Re-enable console interaction on Mac OS X.

Some time after Qt 4.7.4 & Clang 3.1 this stopped working,
always complaining "Read from stdin failed" for no good reason.
Changing from C++ stream to QTextStream is simpler and should be more portable,
but I have only tested under MythBuntu 11.10 and Mac OS X 10.8.4.
Hopefully also OK under Windows?