Add endofline normalisation for JavaScript files.

This should fix issues with ESLint and Grunt tasks on systems that use
line endings other than LF (i.e. Windows systems, using CRLF line
endings).

Closes #2769, #2770.

Author: timwienk

.gitattributes

@@ -0,0 +1 @@
+*.js text eol=lf

Gruntfile.js

@@ -64,6 +64,7 @@ module.exports = function(grunt){
 	}
 
 	grunt.initConfig(config);
+	grunt.util.linefeed = '\n';
 
 	grunt.file.expand('./Grunt/options/*.js').forEach(function(file){
 		grunt.config.merge(require(file)(grunt));