NAME
	Lock -- Lock a directory or file

    SYNOPSIS
	lock  = Lock( name, accessMode )
	D0	      D1	D2

	BPTR Lock(STRPTR, LONG)

    FUNCTION
	A filing system lock on the file or directory 'name' is returned if
	possible.

	If the accessMode is ACCESS_READ, the lock is a shared read lock;
	if the accessMode is ACCESS_WRITE then it is an exclusive write
	lock.  Do not use random values for mode.

	If Lock() fails (that is, if it cannot obtain a filing system lock
	on the file or directory) it returns a zero.

	Tricky assumptions about the internal format of a lock are unwise,
	as are any attempts to use the fl_Link or fl_Access fields.

    INPUTS
	name	   - pointer to a null-terminated string
	accessMode - integer

    RESULTS
	lock - BCPL pointer to a lock

    SEE ALSO
	UnLock(), DupLock(), ChangeMode(), NameFromLock(), DupLockFromFH()