core: add note about color codes "${color:xxx}" in /help weechat.look.day_change_message
core: fix evaluation of expressions with parentheses

First evaluate sub-expressions between parentheses.

Before the fix:
>> 1 && (0 || 0)
== [1]

After the fix:
>> 1 && (0 || 0)
== [0]
Merge branch 'master' of git://git.sv.gnu.org/weechat

Conflicts:
	po/ja.po
logger: add option "flush" for command /logger
translation: update
Merge branch 'master' of git://git.sv.gnu.org/weechat

Conflicts:
	po/ja.po
translation: update