DECRQSS (needed by vttest)

[christianparpart]

trafficstars

DCS $ q Pt ST
          Request Status String (DECRQSS), VT420 and up.
          The string following the "q" is one of the following:
            m       -> SGR
            " p     -> DECSCL
            SP q    -> DECSCUSR
            " q     -> DECSCA
            r       -> DECSTBM
            s       -> DECSLRM
            t       -> DECSLPP
            $ |     -> DECSCPP
            * |     -> DECSNLS
          xterm responds with DCS 1 $ r Pt ST for valid requests,
          replacing the Pt with the corresponding CSI string, or DCS 0 $
          r Pt ST for invalid requests.

Example from vttest \033P$q\"p\033\\

REF: https://vt100.net/docs/vt510-rm/DECSCL.html

Checklist

• [x] DECSCL
• [x] DECSCUSR
• [x] DECSLPP
• [x] SGR
• [x] DECSTBM
• [x] DECSLRM
• [x] DECSCPP
• [x] DECSNLS
• [ ] DECSCA