Inconsistency in description of string literals

[nneonneo]

In the description of various string literals (on lexical-elements.rst):

• RawByteStringContent is specified as taking arbitrary AsciiCharacters. This isn't true - 0x0D (CR) is still rejected, and AsciiCharacter is specified as "any Unicode character in the range 0x00 - 0x7F, both inclusive", without specifically excluding 0x0D. Note that SimpleByteStringLiteral is defined instead in terms of SimpleByteStringCharacter, which is specified to be AsciiCharacter minus 0x0D, 0x22, and 0x5C.
• RawCStringContent is specified as taking any characters except 0x0D (CR) (" ~[\r]* "), but raw C string literals also can't contain 0x00 (NUL).