NAME
        LockLayerInfo -- lock the layerinfo structure.

    SYNOPSIS
        LockLayerInfo( li )
                       a0

        void LockLayerInfo( struct layer_info *);

    FUNCTION
        Before doing an operation that requires the LayerInfo
        structure, make sure that no other task is also using the
        LayerInfo structure.  LockLayerInfo() returns when the
        LayerInfo belongs to this task.  There should be
        an unlocklayerinfo for every locklayerinfo.

        Note: All layer routines presently LockLayerInfo() when they
        start up and unlocklayerinfo() as they exit.  programmers
        will need to use these Lock/Unlock routines if they wish
        to do something with the LayerStructure that is not
        supported by the layer library.

    INPUTS
        li - pointer to layer_info structure

    BUGS

    SEE ALSO
        unlocklayerinfo(), graphics/layers.h