Correct ITER_BUFFERS() macro argument
Large refactor - pull out windows from buffers
Retain init for buffers
Fix right-window evict assertion
Unique buffers across the process
Allow closing of windows with modified non-unique buffers
Add :new and :vnew, and make :sp and :vs use current buffer
Test split-current
Fix :qa test + add :qa-with-:new test
Pull out ^W-[hjkl] to config.h
TODO: k_winmove() window shifting-around stuff
TODO: fix :e - :e/:n now emits a (null)/EFAULT error