introduce CHECK_BUILTIN guard, and replace some unwanted readline with editline.
only force builtin termcap library for the case using builtin editline.
Update uim to 1.8.6.
(now, editline is in pkgsrc, so optionify editline support).

Overview of changes from 1.8.5 to 1.8.6
=======================================
* Fixes
  - libuim
    * Add XDG_RUNTIME_DIR support (by tagoh)
  - po
    * List language names on each line in LINGUAS (by naota)
  - uim-canna
    * Avoid a crash when a Canna server name is specified (by Kouichi ONO)

* Enhancements
  - uim-m17nlib
    * Add an option to set a candidate windows to be visiable or hidden
  - uim-tutcode
    * Updated trycode composition table retrieved 2013-06-26


Overview of changes from 1.8.4 to 1.8.5
=======================================
* Fixes
  - uim-gtk2
  - uim-gtk3
    * Avoid an infinite recursion when no preedit is started (by tagoh)

  - uim-tutcode
    * Fix behavior of postfix katakana conversion
Updated inputmethod/uim to 1.8.6