GN_Fab, Free alarm block

Register parameters

RST 20H, DEFW $6A09

IN:
     BHL = pointer to alarm block

OUT, if call successful:
     Fc = 0
OUT, if call failed:
     Fc = 1
     A = error code:
          RC_BAD ($04), bad alarm block, fatal error

Registers changed after return:
     ...CDE../IXIY same
     AFB...HL/.... different

Related calls

GN_Aab, allocate alarm block
GN_Alp, process an expired alarm (internal OZ usage)
GN_Lab, link an alarm block into the alarm chain
GN_Uab, unlink an alarm block from the alarm chain
OS_Alm, alarm manipulation (internal OZ usage)