NAME
    InitBitMap -- Initialize bit map structure with input values.

SYNOPSIS
    InitBitMap( bm, depth, width, height )
                a0   d0     d1      d2

    void InitBitMap( struct bitmap *, byte, uword, uword );

FUNCTION
    Initialize various elements in the bitmap structure to
    correctly reflect depth, width, and height.
    Must be used before use of bitmap in other graphics calls.
    The Planes[8] are not initialized and need to be set up
    by the caller.  The Planes table was put at the end of the
    structure so that it may be truncated to conserve space,
    as well as extended. All routines that use bitmap should
    only depend on existence of depth number of bitplanes.
    The Flagsh and pad fields are reserved for future use and
    should not be used by application programs.

INPUTS
    bm - pointer to a bitmap structure (gfx.h)
    depth - number of bitplanes that this bitmap will have
    width - number of bits (columns) wide for this bitmap
    height- number of bits (rows) tall for this bitmap

BUGS

SEE ALSO
    graphics/gfx.h