completions for mosh (http://mosh.mit.edu)
Make create_manpage_completions not generate empty files
https://github.com/fish-shell/fish-shell/issues/506
Make io_data_t destructor virtual
Introduce a macro cast_init to abbreviate common static_cast's a bit

This macro doesn't work with type names containing commas, but that doesn't
seem to be too common in fish.
Let io_data_t constructor take optional io_mode and fd
Merge branch 'master' into oo-io-volatile
Put io_data_t detail printing in virtual io_data_t::print
parser.cpp: Put off initialization of new_io until mode is known
Split out io_close_t.