Reference for unit 'charset': Procedures and functions

`getascii`		Convert unicode character or string to single-byte character or string.
`getmap`		Find a codepage map
`getunicode`		Map single-byte character to unicode character.
`loadbinaryunicodemapping`		Load binary single-byte codepage to unicode map from file or memory
`loadunicodemapping`		Load textual single-byte codepage to unicode map from file
`mappingavailable`		Check if a mapping is available for a specified code page.
`registerbinarymapping`		Load and register binary single-byte codepage to unicode map from file
`registermapping`		Register mapping