NSS validity check is too rigid

[claussni]

The NSS validity check doesn't allow for certain characters. Specification says different (RFC 2141, section 2.2)

<NSS>         ::= 1*<URN chars>

   <URN chars>   ::= <trans> | "%" <hex> <hex>

   <trans>       ::= <upper> | <lower> | <number> | <other> | <reserved>

   <hex>         ::= <number> | "A" | "B" | "C" | "D" | "E" | "F" |
                     "a" | "b" | "c" | "d" | "e" | "f"

   <other>       ::= "(" | ")" | "+" | "," | "-" | "." |
                     ":" | "=" | "@" | ";" | "$" |
                     "_" | "!" | "*" | "'"

[dmarkov]

@yegor256 dispatch this issue please