Import completion updates from tmux.git, the revision used was
c67abcf8182b, and the updates were generated by Util/check-tmux-state.
check-tmux-state: changes to output parsing + variable declaration
parsing of `tmux show-options` is slightly more idiomatic (thanks to
@phy1729 for the syntax), and it now also ignores user-specified options
(which are prefixed with an @ symbol).
the lines defining and declaring supported_server_options were also
swapped to the correct order - `typeset` was being called after
supported_server_options was populated, contrary to all the other
supported_*/available_* arrays used in the same area of the file.
In 580698bc71, Oliver updated a whole bunch of options in a number of
completions. While at it, he also changed a bit of coding style, to
better adhere to Etc/zsh-development-guide — among those changes is to
convert "function foobar() {" function definitions to "foobar() {".
This broke Util/check-tmux-state so that it couldn't detect any
supported tmux sub-commands within _tmux anymore. This updates the
regular expression that is used in the script to match and list these
function definitions.
