sysutils/linuxfdisk: use better PROC_PARTITIONS path on FreeBSD

Originating from GNU/Linux, this code had naturally defined the
PROC_PARTITIONS macro as "/proc/partitions", while we typically
mount this file system under "/compat/linux/proc/partitions" on
FreeBSD. Fix two (out of four) definitions which appear in the
generated executables, so e.g. `sfdisk-linux -s' would now work
correctly so long as linprocfs(5) is mounted. While at it, set
the LICENSE (GPLv2+) and bump PORTREVISION so users could enjoy
less buggy package.

PR: 257072