added relativenumber option

fix XVim.option.m
Fix for Xcode 5.1 build support
Merge pull request #552 from tonyd256/td-xcode51-fix

Quick fix for Xcode 5.1 build support
Merge pull request #544 from toliuweijing/features/relativenumber2

[relativenumber]add relativenumber
Set default relativenumber to NO
Use number option when using relativenumber option