'hg status -q' output skips non-tracked files.
The '-q' flag was ignored in status command. But this flag
can be used to hide non-tracked files in hg status output.
This small correction makes status command more general,
similar to 'svn status', where '-q' flag has the same effect.
The '-u' and '-A' flags have priority over '-q'.
A testcase and doc-string for status was extended to cover
'-q' flag.