INT 15 - DESQview 2.50+ - SEND MESSAGE - "GETNAME" - GET NAME OF MAILBOX
        AH = 12h
        BH = 12h
        BL = mailbox for which to retrieve name
            00h DWORD on top of stack is mailbox handle
            02h use given task's mailbox (task's handle on top of stack)
            03h use current task's default mailbox
        STACK: DWORD length of buffer for name
               DWORD pointer to buffer
Return: STACK: DWORD length of returned name (or size of buffer, if less)
Program: DESQview 2.5x is distributed as part of DESQview/X 1.0x
Note:   the returned name is not NUL-terminated
SeeAlso: AX=DE0Eh