/**
 *
 * Scanner::remove_charset
 *
 * Forget about a registered charset encoding.
 *
 * Throws a RuntimeError if LMS is unable to remove the charset.
 *
 * * p1 (charset) charset name as understood by iconv_open(3).
 *
 * * return charset
 *
 */
static VALUE scanner_remove_charset(VALUE self, VALUE charset) {