Opens a muxwait semaphore.

#define INCL_DOSSEMAPHORES
#include <os2.h>

PSZ       pszName;  /*  A pointer to the ASCIIZ name of the semaphore to open. */
PHMUX     phmux;    /*  Pointer to a muxwait-semaphore handle. */
APIRET    ulrc;     /*  Return Code. */

ulrc = DosOpenMuxWaitSem(pszName, phmux);