luci-base: use serialize_json() in luci.http

Signed-off-by: Jo-Philipp Wich <jow@openwrt.org>

modules/luci-base/luasrc/http.lua

@@ -285,40 +285,5 @@ urlencode = protocol.urlencode
 --- Send the given data as JSON encoded string.
 -- @param data		Data to send
 function write_json(x)
-	if x == nil then
-		write("null")
-	elseif type(x) == "table" then
-		local k, v
-		if type(next(x)) == "number" then
-			write("[ ")
-			for k, v in ipairs(x) do
-				write_json(v)
-				if next(x, k) then
-					write(", ")
-				end
-			end
-			write(" ]")
-		else
-			write("{ ")
-			for k, v in pairs(x) do
-			write("%q: " % k)
-				write_json(v)
-				if next(x, k) then
-					write(", ")
-				end
-			end
-			write(" }")
-		end
-	elseif type(x) == "number" or type(x) == "boolean" then
-		if (x ~= x) then
-			-- NaN is the only value that doesn't equal to itself.
-			write("Number.NaN")
-		else
-			write(tostring(x))
-		end
-	else
-		write('"%s"' % tostring(x):gsub('["%z\1-\31]', function(c)
-			return '\\u%04x' % c:byte(1)
-		end))
-	end
+	util.serialize_json(x, write)
 end