These functions provide additional support to control the appearance of
presentation graphics elements.

The following functions are defined:

_pg_getchardef
    get bit-map definition for a specific character

_pg_getpalette
    get presentation graphics palette (colors, line styles, fill patterns
    and plot characters)

_pg_getstyleset
    get presentation graphics style-set (line styles for window borders and
    grid lines)

_pg_hlabelchart
    display text horizontally on a chart

_pg_resetpalette
    reset presentation graphics palette to default values

_pg_resetstyleset
    reset presentation graphics style-set to default values

_pg_setchardef
    set bit-map definition for a specific character

_pg_setpalette
    set presentation graphics palette (colors, line styles, fill patterns
    and plot characters)

_pg_setstyleset
    set presentation graphics style-set (line styles for window borders and
    grid lines)

_pg_vlabelchart
    display text vertically on a chart