BHL = pointer to alarm block (to be linked).
Must have been previously allocated by GN_Aab.
OUT, if call successful:
Fc = 0
OUT, if call failed:
Fc = 1, time/date already passed
A = error code:
RC_BAD ($04), bad parameters
Registers changed after return:
A badly formed block is likely to crash the machine. The routine does not check the vality of the alarm block.
GN_Aab, allocate alarm block
GN_Alp, process an expired alarm (internal OZ usage)
GN_Fab, free alarm block
GN_Uab, unlink an alarm block from the alarm chain
OS_Alm, alarm manipulation (internal OZ usage)