fix json support since Steve Teuber's patches were outdated

- add json support to games added since Steve Teuber's patches
- use xform_names instead of name_xforms since Steven Hartland's refactoring
- use xform_printf() instead of fprintf() for json output
- remove commented out code
- use %s for a const switch seems a bit wasteful, fixing it
- do not use inline tests
- explicitely test pointers with NULL
- escape lone backslash character too
- RFC 4627 says: “JSON text SHALL be encoded in Unicode. The default encoding is UTF-8.”