fix url paths escape bug in dumpLineNumbers function  

less node modules in windows system ,path sep is '\',the old regexp is not match it. I whrite a new regexp and fix it;
example:
url: "file://D:\workspace\test\style.less";
error result: "file\:\/\/C\:\workspace\test\style\.less", it's not replace "\";
the right result is: "file\:\/\/D\:\/workspace\/test\/style\/.less",replace "\" to "\/";