Method readPcodeSnippet

\brief Scan a single-line p-code snippet declaration from the given stream A declarator is scanned first, providing a name to associate with the snippet, as well as potential names of the formal \e output Varnode and \e input Varnodes. The body of the snippet is then surrounded by '{' and '}' The snippet name, input/output names, and the body are passed back to the caller. \param s is the given