Redmine

Following #21375#note-11, I made four additional (code) documentation changes:

1. Complement external URL documentation. posted as #21375#note-11
2. Fix typo in detailed Japanse textile doc. (the closing angle bracket seems superfluous)
3. Add user link documentation. (detailed syntax doc; this was still missing from #4179)
4. Fix code doc indentation. (in ApplicationHelper#parse_redmine_links)
5. Add code doc for forum & news links. (in ApplicationHelper#parse_redmine_links; this was missing from #9600)

I'll attach the four remaining patches implementing these changes. The patch serial, against current source:/trunk@16676, is produced using git format-patch which makes it apply-able using "patch -p1 < 0001-...". This serial is a continuation of #21375#note-11 which includes patch 1/5 of this set, making these patches dependent on #21375#note-11 integration.
I'll also change the respective wiki pages accordingly when the patches have been committed.

Environment:

Environment:
  Redmine version                3.3.3.devel@r16676
  Ruby version                   2.3.3-p222 (2016-11-21) [x86_64-linux]
  Rails version                  4.2.8
  Environment                    production
  Database adapter               Mysql2
SCM:
  Subversion                     1.8.8
  Git                            1.9.1
  Filesystem                     
Redmine plugins:
  no plugin installed