Merge branch 'refs/heads/t/doc-improvements'

Another topic branch that was cooking for far too long.

* refs/heads/t/doc-improvements:
  Switch from grutatxt to markdown.
  INSTALL: Link to the gengetopt web page.
  manual: Fix a whitespace issue.
  manual: Add example for interactive mode.
  manual: Add two more examples.
  manual: Add example query for omitting a directory.
  manual: Add short option example.
  manual: Remove pointless "time" prefix.
  manual: Improve documentation of --output.

diff --combined Makefile
index 58202a224a6634ed39288ccf3b44f263ee715fb7,b5cfebd74b0b4c5c073be2635cc8f1b2d8681536..8e4d65388c3576aaf64a729cd6e710b2c9724156
--- 1/Makefile
--- 2/Makefile
+++ b/Makefile
@@@ -72,13 -72,13 +72,13 @@@ adu.1: adu adu.1.in
        man2html $< | sed -e 's|^<DT><DD>$$|<DT><DD><br>|g' > $@
  
  clean:
 -      rm -f *.o adu *cmdline.c *cmdline.h adu.1 adu.1.html adu.png index.html adu.sk~
 +      rm -f *.o adu *cmdline.c *cmdline.h adu.1 adu.1.html index.html
  
  index.html: adu.1.html index.html.in INSTALL README
        sed -e '/@README@/,$$d' index.html.in > $@
-       grutatxt -nb < README >> $@
+       markdown README >> $@
        sed -e '1,/@README@/d' -e '/@INSTALL@/,$$d' index.html.in >> $@
-       grutatxt -nb < INSTALL >> $@
+       markdown INSTALL >> $@
        sed -e '1,/@INSTALL@/d' -e '/@MAN_PAGE@/,$$d' index.html.in >> $@
        sed -e '1,/Return to Main Contents/d' -e '/Index/,$$d' adu.1.html >> $@
        sed -e '1,/@MAN_PAGE@/d' index.html.in >> $@