Most problems are fixed (or rather worked-around) by making long '====='
separators pre-formatted (i.e. prefixed with two spaces).  In order to
preserve visual view, the code examples themselves are prefixed with 3
spaces.

This commit fixes the following man warnings:

$ cmake --help-man - | LANG=C MANWIDTH=80 man --warnings -l - > /dev/null
  <standard input>:6024: warning [p 105, 1.7i]: can't break line
  <standard input>:6027: warning [p 105, 2.7i]: cannot adjust line
  <standard input>:6027: warning [p 105, 2.8i]: can't break line
  <standard input>:7142: warning [p 117, 7.8i]: can't break line
  <standard input>:7171: warning [p 117, 11.8i]: can't break line
  <standard input>:8878: warning [p 136, 9.0i]: can't break line
  <standard input>:8887: warning [p 136, 11.5i]: cannot adjust line
  <standard input>:8887: warning [p 136, 11.7i]: can't break line
  <standard input>:8904: warning [p 136, 14.2i]: can't break line

Patch from Modestas Vainius.  See issue #9659.