Fix CT_SanitizePath

Replace the over-engineered and buggy test in CT_SanitizePath
with a straight forward string pattern match, and also
handle empty PATH elements which are qeuivalent to ".".

Thanks-To: Arnaud Lacombe <lacombar@gmail.com>
Signed-off-by: Johannes Stezenbach <js@sig21.net>

 reporter_name="Harold Grovesteen"

 reporter_url="http://sourceware.org/ml/crossgcc/2009-11/msg00052.html"

 reporter_comment=""