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/math/wrap_Math.cpp

@@ -357,7 +357,7 @@ int w_compress(lua_State *L)
 	Compressor::Format format = Compressor::FORMAT_LZ4;
 
 	if (fstr && !Compressor::getConstant(fstr, format))
-		return luaL_error(L, "Invalid compressed data format: %s", fstr);
+		return luax_enumerror(L, "compressed data format", Compressor::getConstants(format), fstr);
 
 	int level = (int) luaL_optinteger(L, 3, -1);
 
@@ -399,7 +399,7 @@ int w_decompress(lua_State *L)
 		const char *fstr = luaL_checkstring(L, 2);
 
 		if (!Compressor::getConstant(fstr, format))
-			return luaL_error(L, "Invalid compressed data format: %s", fstr);
+			return luax_enumerror(L, "compressed data format", Compressor::getConstants(format), fstr);
 
 		size_t compressedsize = 0;
 		const char *cbytes = nullptr;