Consider using "strict mode" in jsoncpp

[axic]

  /** \brief A configuration that is strictly compatible with the JSON
   * specification.
   * - Comments are forbidden.
   * - Root object must be either an array or an object value.
   * - Assumes Value strings are encoded in UTF-8
   */
  static Features strictMode();

This would be used for parsing incoming "standard json input".

[axic]

1. libsolidity/interface/StandardCompiler.cpp must be changed to enforce strict mode
2. tests at test/libsolidity/StandardCompiler.cpp need to be added to ensure strict mode actually works