Convert the lockstat(1) man page to mdoc and make sure that it gets
installed. Additionally, remove Solaris-specific sections and references,
and replace example outputs with output from lockstat on FreeBSD, since
lockstat's output contains stack traces.

This change also removes some examples that don't seem to work properly on
FreeBSD. The examples should be re-added when lockstat is fixed.

Reported by: avg
MFC after: 1 week