fcntl).
lock/unlock/sopen for Unix now use both lockf and fcntl mechanisms
Replaced C++ comments with C comments.

(destroying an invalid critical section on Win32 is bad).
Only call TerminateProcess once if successful (5 seconds after hang-up detect).
Frequent checking of process exit code when hang-up detected.

with EX_OFFLINE mode bit set (don't care if user hung-up).

Added AuthViaIpCheckBox which allows authentication (for relay) via POP3
or other protocol within the last 60 minutes (this was previously always
enabled if authenticated-relay was allowed, but now that we have real SMTP
AUTH support, this less-secure method is optional).

Created system.lastuser property to get last user record number.
Updated property and method descriptions.
system.secondstr() returns null if no argument specified.

before common global functions).
Updated global method descriptions.

before common global functions).