Remove the OK and ERR macros. They obfuscate the code and don't

Remove the OK and ERR macros. They obfuscate the code and don't
help legibility. (unix system calls use 0 for ok, but hundreds of
other projects use 1 to indicate success.) Despite the name, many
system calls (e.g., open) also return not OK values for success.
It also cleans up some weird code like int crontab_fd = OK - 1;
This diff is mechanical in nature. Later I will fix the bugs it reveals.
ok deraadt