Improving matching of ISO 6709 GPS format

ISO 6709 format dictates that the format includes characters ° (degree),
' and ". If we only test for the coordinates starting with decimal, we
match also the decimal notation on this test. Thus adding test for the
degree sign not to match input as ISO 6709 when coordinates are given in
decimal notation.

Signed-off-by: Miika Turkia <miika.turkia@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>