mk: fix for Unix build

acme: fix double-free in acmeerrorproc The receiver of cerr takes ownership of s.

mount: find kext with MacFUSE >=4 and macOS >=11

9pfuse: support MacFUSE >=4 MacFUSE 4 removes support for passing device fd to the mount command. Adds support for the receiving the fd over a socket instead, and updates command paths and filesystem name.

9p: parse lines in rdwr command Use bio(3) to read at most one line of input per iteration, even if there is more than one line available in the input buffer. This makes it easier to interact with line-oriented ctl files like that of factotum(4) from shell scripts, without the need to control when and how much data is flushed to a pipe.

man9: rename IM to MR Commit d32deab17bfffa5bffc5fab3e6577558e40888c5 renamed IM to MR but these man pages were missed.

htmlroff: fix array bounds

eqn: enlarge errbuf to account for large tokens

xd: fix swizz8 loop counting

libhtml: fix array bounds in lex

libthread: call setpgrp in programs that will background This fixes the 'run stats from rc; exit rc; stats dies' problem. It's unclear whether this is the right fix or whether rc should be starting all its interactive commands in their own process groups. But at least it does fix stats dying.

sam: avoid out-of-bounds read in rterm Usually r->nused < r->nalloc and the read is in bounds. But it could in theory be right on the line and reading past the end of the allocation. Make it safe but preserve as much of the old semantics as possible. This use of rterm appears to be only for optimization purposes so the result does not matter for correctness.

sam: remove backward ?: The exit code here is ignored anyway.

rc: do not exit on EINTR from read This happens if lldb attaches to rc.

lib9: reject postnote with special pids