This routine contains a Windows message loop. It is called automatically by
ClearWin+ so that the programmer does not need to include a message loop in a
program. It can be used within a program to ensure that a process does not
totally take over the CPU. OPTION may be either Y_PERMANENTLY or Y_TEMPORARILY.
You may need to call this routine using Y_TEMPORARILY, if the program makes
protracted use of the CPU and you want to allow it to respond to events (such
as mouse events) whilst the processing continues. Call this routine at suitable
points during the process to enable the message queue for the current
application to be processed. (Message queues for other applications that are
running will automatically be processed because Windows 95 and Windows NT are
pre-emptive multi-tasking operating systems.) TEMPORARY_YIELD@() is the same as
Calling this routine using Y_PERMANENTLY is equivalent to reaching the END
statement of a ClearWin+ program.