loader: Change version calculation to be more consistent.

Use 1000 * major + minor when calculating the version number that
gets set in the Ficl environment or lua loader property. This allows
for more room if the minor number needs to go above 9.

Add loader.version property to lua loader.

PR: 282001
Reviewed by: imp
Obtained from: Juniper Networks, Inc.
Differential Revision: https://reviews.freebsd.org/D39631

(cherry picked from commit a50d73d5782a351ad83e8d1f84d11720a12e70d3)