i3bar: fix resource leak: statusline_ctx needs to be freed first

In practice this is rarely noticeable, unless you very often switch
screen resolutions, I think.

fixes #1172
Merge branch 'fix-i3bar-leak'
Bugfix: ipc_receive_message reply leak

The function ipc_recv_message in libi3 allocates memory to the location
of the `message` reply in src/ipc_receive_message.c with malloc and must
be freed.

This memory leak was found using valgrind.
Merge branch 'fix-recv-memleak'
Bugfix: don't try to resize docks by command

cmd_resize does not implement a method to resize dock clients.

A command like `[instance=".*"] resize grow width 160 px or 16 ppt`
when a dock client matched would crash i3.

fixes #1201
Merge branch 'fix-resize'