Fix https://github.com/krakjoe/phpdbg/issues/91

Enable edit feature when build with libedit.

Notice: coloured prompt only enable with READLINE
Better fix for phpdbg + libedit
- fix include
- disable coloured prompt only with libedit
Merge branch 'PHP-5.6'

* PHP-5.6:
  Better fix for phpdbg + libedit - fix include - disable coloured prompt only with libedit
  Fix https://github.com/krakjoe/phpdbg/issues/91