[freebsd91p7][vim] Disable YCM by default.

How to enable YCM one-time:
$ VIM_DISABLE_YMC=0 vi
Merge remote-tracking branch 'origin/cygwin' into freebsd91p7
[freebsd91p7] New local pkg for gnu ls (supports --color options).
Merge remote-tracking branch 'origin/cygwin' into freebsd91p7
[freebsd91p7][vim] viv to show startup time after vim started.