MFC: stand: liblua: add a pager module

MFC: stand: liblua: add a pager module

This is nearly a 1:1 mapping of the pager API from libsa.  The only real
difference is that pager.output() will accept any number of arguments and
coerce all of them to strings for output using luaL_tolstring (i.e. the
__tostring metamethod will be used).

The only consumer planned at this time is the upcoming "show-module-options"
implementation.

(cherry picked from commit 0a0d522b368b31ec51611b798047a75b52855f39)