Import bmake-20220330
Most relevant change:
o parse.c: try to include 'posix.mk' the first time
.POSIX: is encountered, to allow for beter POSIX compliance.
Others
o cond.c: make debug logging for comparisons less technical
o lst.c: fix mem leak in Lst_Remove
o job.c: fix echoing of command with '-' in silent target in jobs mode
o var.c: make debug logs more readable
prefer 'long long' over 'long' on 32-bit C99 platforms
fix crash on .undef of an environment variable