uric/contact: fix display name and contact header uri escaping

[maximilianfridrich]

In re, display names are always sent as quoted-string which must not be escaped. Further, basically all UTF-8 characters are allowed in quoted-strings, so not checking it should be fine for almost all cases. The relevant rules in the BNF of RFC 3261 section 25.1:

      UTF8-NONASCII   =  %xC0-DF 1UTF8-CONT
                      /  %xE0-EF 2UTF8-CONT
                      /  %xF0-F7 3UTF8-CONT
                      /  %xF8-Fb 4UTF8-CONT
                      /  %xFC-FD 5UTF8-CONT
      UTF8-CONT       =  %x80-BF

      quoted-string  =  SWS DQUOTE *(qdtext / quoted-pair ) DQUOTE
      qdtext         =  LWS / %x21 / %x23-5B / %x5D-7E
                        / UTF8-NONASCII
      quoted-pair  =  "\" (%x00-09 / %x0B-0C
                      / %x0E-7F)

      display-name   =  *(token LWS)/ quoted-string

So the special character 0x00-0x20 (execpt LWS), 0x7F, '', '"', CR and LF are not allowed. And the quoted-pair rules even allows '"' and '\' (and any other ASCII character except for CR and LF) as long as they are preceded by a '\'.

Also, SIP URIs in the Contact header must be escaped.

[cspiel1]

Looks good to me.

Escaping URI parameters will be handled in a separate PR.

[cspiel1]

Then we should remove uri_display_name_escape() completely. It is currently not used.

[cspiel1]

We shortly added this function. So most likely nobody depends on it.
The PR looks good for me.

[alfredh]

I think this one looks ready for merge ...