Add math.round and fix vector.round (#10803)

builtin/common/misc_helpers.lua

@@ -244,6 +244,15 @@ function math.factorial(x)
 	return v
 end
 
+
+function math.round(x)
+	if x >= 0 then
+		return math.floor(x + 0.5)
+	end
+	return math.ceil(x - 0.5)
+end
+
+
 function core.formspec_escape(text)
 	if text ~= nil then
 		text = string.gsub(text,"\\","\\\\")

builtin/common/vector.lua

@@ -41,9 +41,9 @@ end
 
 function vector.round(v)
 	return {
-		x = math.floor(v.x + 0.5),
-		y = math.floor(v.y + 0.5),
-		z = math.floor(v.z + 0.5)
+		x = math.round(v.x),
+		y = math.round(v.y),
+		z = math.round(v.z)
 	}
 end