Use new node recursive file watching in tsserver

[mhegazy]

courtesy of @billti

Recursive directory watching for Windows and OSX is landing in node master: nodejs/node#2649

This enables watching a folder recursively on Windows (was already available on OS X). Under the covers this is a change in libuv (which abstracts away the OS) and uses the ‘watchSubtree’ option on the Win32 ReadDirectoryChanges function – so it should be highly reliable. (libuv change viewable here).

[dhusemann]

Looks like it will be in node.js 4.0 and backported to IO.js 3.3.1.

[zhengbli]

That means we can get rid of our own pollling mechanism currently in use for file watching? What about users who uses a lower node version?

[mhegazy]

We should do feature detection. I think it is fine for new features like watching directories for new files to work on node 4 only.

[zhengbli]

Another question is, where should we start the directory watching? If we start from the root level (e.g. "C:"), we will have to respond to a lot of system file changing events (temp file creating, other app updating their files, OneDrive syncing etc.) that is pure noise to us; if we start from the current path, we may miss when the user adds a tsconfig file in an upper level directory.

[zhengbli]

Fixed with #5127