Show (short) list of possible enum values when an invalid value is encountered (resolves #1318)

All enum errors have (hopefully) been changed to a luax_enumerror, which has a
fixed error message. If additionally a list of valid options is passed, it
lists that in the error message. For every enum error with few options I've
implemented this using a getConstants call.

This solution has been designed specifically to reduce the number of template
instantiations (as I've been told that was a concern). All new template code
happens in places where there already was an instantiation of the relevant
StringMap. Of course there is still std::vector<std::string>...

--HG--
branch : minor

src/modules/data/wrap_CompressedData.cpp

@@ -47,7 +47,7 @@ int w_CompressedData_getFormat(lua_State *L)
 
 	const char *fname = nullptr;
 	if (!Compressor::getConstant(t->getFormat(), fname))
-		return luaL_error(L, "Unknown compressed data format.");
+		return luax_enumerror(L, "compressed data format", Compressor::getConstants(Compressor::FORMAT_MAX_ENUM), fname);
 
 	lua_pushstring(L, fname);
 	return 1;