This patch series prepares the Linux man-pages for migration from
font-related macro calls like `BR` to typeset man page cross references
to the `MR` macro used by groff 1.23.0 (and which originally appeared in
Plan 9 from User Space troff's man(7) package).

To read more about why `MR` exists, and its advantages over font-based
macro calls for man page cross references see the groff 1.23.0 release
notes.

https://git.savannah.gnu.org/cgit/groff.git/tree/NEWS?h=1.23.0#n237

In particular, this series converts man page cross references inside
tbl(1) tables, which have a more complex textual context (in man(7)
source) than most others.

Signed-off-by: "G. Branden Robinson" <redacted>