Move get_self_executable_path() into "os.h"/os.c
Fix bug in read_symlink(), improve logging
Improve "log.h", make logMessage() inline

Make logMessage() -- wrapper around vlogMessage() -- an inline
function and remove redundant conditional level != LOG_LEVEL_SILENT

Move logString() into log_util.c, refactor so outer loop now iterates
over lines in buffer, rather than over all log outputs

Rename log_backtrace() to logBacktrace() for consistency

Document __NOWHENCE__ value
Improve mdp_recv() error handling

Make all V2 MDP interface calls take a __whence argument

mdp_recv() always sets error before returning -1, does not set
errno=0 otherwise

mdp_recv() does not log errors on EINTR or EAGAIN (EWOULDBLOCK)

mdp_recv() sets errno=EOVERFLOW if local socket name is too long

mdp_recv() sets errno=EBADMSG if malformed or spurious packet
received

Remove redundant mdp_recv() error logging from "mdp ping" and
"config sync" and several "id" commands