www/node6: build on FreeBSD >=12

Change the default options to enable BUNDLED_SSL by default on
FreeBSD >=12, which includes OpenSSL 1.1 in the base system, not the
1.0.2 required by Node.js 6.x LTS. Bump PORTREVISION due to the change
in defaults.

While here, convert the port to use BROKEN_SSL, taking care to set
BROKEN_SSL+=base when appropriate.

Sponsored by: Miles AS