Fixes #334.

`window:willUseFullScreenPresentationOptions:` is an instance method of the protocol `NSWindowDelegate`.

Fixes #332.

There are many things we could do to make this work. an environment variable to control the character. Another option would be to use U+00A0 (non-breaking space), which renders the same as space. This change avoids changing the separator character and instead assumes that if the left side of the tag already ends in " Del Snarf |" then what comes before that is the file name. Acme already aggressively preserves the "Del Snarf |", so this should work decently well as a stop-gap. We can always try something else later. Fixes #26. Fixes #104. Fixes #329.

Avoid signed integer overflow using ulong instead of long h.

Real disk devices should be block devices anyway. One user reported the disksize check causing a system reboot during vac of a tree with an "interesting" device. Fixes #103.

This brings mk's behavior when using rc in line with Plan 9's. The existing code is for Unix environment data structures but also was assuming Unix shell semantics where empty and missing variables are mostly equivalent. The Plan 9 code (/sys/src/cmd/mk/plan9.c in the distribution) explicitly removes /env/name (creating an empty list) when the value is missing or an empty string. Fixes #255.

Fixes #233.

Fixes #9. Fixes #219. Fixes #222. Fixes #330.

When a directory has lots of children, vac crashes because it runs out of cache. Fixes #266.