Add NEWS about uim-xim.

* NEWS
  - (Overview of changes from 1.8.3 to 1.8.4):
    Add Enhancements about uim-xim.
Add a section for 1.8.5.

* NEWS
  - (Overview of changes from 1.8.4 to 1.8.5): New section.
Add NEWS about uim-tutcode.

* NEWS
  - (Overview of changes from 1.8.4 to 1.8.5):
    Add fix about uim-tutcode.
Add NEWS about uim-gtk.

* NEWS
  - (Overview of changes from 1.8.4 to 1.8.5):
    Add a fix on uim-gtk.
Add a section for 1.8.6.

* NEWS
  - (Overview of changes from 1.8.5 to 1.8.6): New section.
Add an item on uim-tutcode to NEWS.

* NEWS
  - (Overview of changes from 1.8.5 to 1.8.6): Add an item on uim-tutcode.
Add contributors' name to NEWS.

* NEWS
  - (Overview of changes from 1.8.5 to 1.8.6): Add contributors' name.
Update RELNOTE.

* RELNOTE
  - Update from 1.8.4 to 1.8.5.
Update RELNOTE.

* RELNOTE
  - Update from 1.8.5 to 1.8.6.
Change a sentence in RELNOTE.

* RELNOTE
  - Change a sentence.
Update RELNOTE.

* RELNOTE
  - Update.