Merge branch 'ma/asciidoctor-build-fixes'

A topic to optionally build with meson, which has graduated to
'master' recently, broke Documentation pipeline with asciidoctor
for the normal Makefile build as well as meson-based one, which
have been corrected.

* ma/asciidoctor-build-fixes:
  asciidoctor-extensions.rb.in: inject GIT_DATE
  asciidoctor-extensions.rb.in: add missing word
  asciidoctor-extensions.rb.in: delete existing <refmiscinfo/>