Ticket 466: case folding of character names

In ticket #11 we voted to make the reader case-sensitive by default. In ticket #92 we further added the R6RS #!fold-case and #!no-fold-case reader extensions. In both cases the terminology was lax and simply referred to "reader case sensitivity", and all discussion centered around symbols, although in R6RS character names were also effected.

Case folding will apply to numeric literals, booleans and bytevectors regardless, as they do in both R5RS and R6RS. We need to clarify how character names and the case folding directives themselves are handled.

See http://www.r6rs.org/final/html/r6rs-app/r6rs-app-Z-H-4.html#node_chap_B