core: add functions to manage array lists
core: add extra check on arraylist pointer in arraylist functions
core: reset data contents in function arraylist_clear if size_alloc_min > 0
core: add comment about argument "index" of function arraylist_search
tests: add tests of arraylist functions
core: optimize completion by using arraylists

With arraylist (vs weelist), the completion is about 50x faster.
It is visible on "/help [+tab]".
core: use a sorted arraylist for partial completions

With a sorted list, the partial completion is about 50x faster
(like other completions).
aspell: fix compilation with enchant version older than 1.6.0 (closes #192)
trigger: do not allow any changes on a trigger when it is currently running (closes #189)
doc: update Polish auto-generated files
guile: fix compilation with Guile < 2.0.4 (closes #198)
core: fix sentence in ChangeLog
core: update German translations
core: fix compilation of plugin API functions (macros) when compiler optimizations are enabled (closes #200)
core: fix highlight of IRC action messages when option irc.look.nick_mode is set to "action" or "both" (closes #206)
core: update German translations
irc: fix type of value stored in hashtable when joining a channel (closes #211)
core: fix crash on buffer close when option weechat.look.hotlist_remove is set to "merged" (closes #199)
relay: fix send of signals "relay_client_xxx" (closes #214)

The signals about relay client status changes were sent only when the client
has ended. Now it is went on any status change.
doc: add instructions for compilation with Homebrew in user's guide and FAQ