Add \FR on lines that start with \FB as it is likely useful, but not
stricly necessary. However if there is just \ the line won't render at
all as happened in example below from 'man mysql-test-test.pl.1':

  AUTHOR
         MariaDB Foundation (http://www.mariadb.org/).
                                                 MYSQL-TEST-RUN()
  ->
  AUTHOR
         MariaDB Foundation (http://www.mariadb.org/).
  MariaDB 10.11        15 May 2020              MYSQL-TEST-RUN(1)

Also use full command name instead of truncated ones.

All new code of the whole pull request, including one or several files
that are either new files or modified ones, are contributed under the
BSD-new license. I am contributing on behalf of my employer Amazon Web
Services, Inc.