Update to 1.8

uname -r shows 4 formats.
9.0-BETA1, 9.0-RC1, 9.0-RELEASE, and 9.0-RELEASE-p1
Logic added by 1.7 was supposed to correctly remove the -p1 string,
which it did if present, but if not present the -RELEASE gets removed
in error which results in the incorrect ftp url path for fetching the
install source.

Rewrote logic to handle -p suffix differently so it gets stripped
off leaving 9.0-RELEASE which is handled normally.

PR: ports/174037
Submitted by: Joe Barbish <qjail@a1poweruser.com> (maintainer)
Feature safe: yes