Currently, when port version is set to a GitHub sub-version (ex. DISTVERSION=1.0.0-35), PORTVERSION becomes 1.0.0.35 which
presents users with a version number that hasn't been defined by the project (1.0.0.35). The project only defined 1.0.0.
On the other hand, sub-versions are often necessary either because released versions don't build for various reasons, or because
fixes that were committed later need to be included, or simply because some projects just stop making releases, or don't make them
for a very long time.
To solve this, the attached patch adds a letter 'm' to the revision part of the PORTVERSION, making PORTVERSION=1.0.0.m35, for the above example.
This would be beneficial for all users, and also particularly for repology, because it primarily needs to know versions that FreeBSD ports are for, to
be able to compare version numbers with versions that other systems have.