docs: ascii version of manpage without nroff

docs: ascii version of manpage without nroff

Create ASCII version of manpage without nroff

 - build src/tool_hugegelp.c from the ascii manpage
 - move the the manpage and the ascii version build to docs/cmdline-opts
 - remove all use of nroff from the build process
 - should make the build entirely reproducible (by avoiding nroff)

 - partly reverts 2620aa9 to build libcurl option man pages one by one
   in cmake because the appveyor builds got all crazy until I did

The ASCII version of the manpage

 - is built with gen.pl, just like the manpage is
 - has a right-justified column making the appearance similar to the previous
   version
 - uses a 4-space indent per level (instead of the old version's 7)
 - does not do hyphenation of words (which nroff does)

History

  We first made the curl build use nroff for building the hugehelp file in
  December 1998, for curl 5.2.

Closes #13047