Issue #8746: Correct faulty configure checks so that os.chflags() and

Issue #8746: Correct faulty configure checks so that os.chflags() and
os.lchflags() are once again built on systems that support these
functions (*BSD and OS X).  Also add new stat file flags for OS X
(UF_HIDDEN and UF_COMPRESSED).  Also add additional tests for
os.chflags() and os.lchflags(). (Tests by Garrett Cooper)