Added support for separate executable and library output directory (object files are not compatible due to imported symbols).

Only exported function prototypes are now included in sbbs.h when included from external module (e.g. ftpsrvr.c).

This is apparently the only way to generated MSVC __cdecl-compatible names.
The stack maintenance isn't supposed to be compatible, but it appears to work. <shrug>

Reverted back to macro bethod of testing sizeof(node_t). Some compilers (e.g. MSVC) resolve sizeof() after preprocessing.

Import libraries (e.g. sbbs.a) are put in the output directory along with the .o files.

Moved common variable definitions (OBJS, HEADERS, and SBBSDEFS) into separate include (*.mak) files.
Moved dependencies into depends.mak (great name, huh?).

Included by Makefile.bor and Makefile.gnu (right now).

Displays startup time using lprintf for time-zone verification.
cleanup() doesn't call WSACleanup unless WinSock has been initialized.
A bit more diagnostic output in send_file routine.

Displays startup time using lprintf for time-zone verification.
cleanup() doesn't call WSACleanup unless WinSock has been initialized.