Send error messages to stderr rather than stdout

Send error messages to stderr rather than stdout

The commit changes printf's that output error and warning messages to
send their text to the stderr stream.  Non-error output, such as that
produced by passing the -help option to a test, still goes to stdout.

Change-Id: Iea4d62451e3e7e84c654859cb09ea7e717511d13
Reviewed-on: http://codereview.qt.nokia.com/3636
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Rohan McGovern <rohan.mcgovern@nokia.com>