Added a needed feature to winfsnotify

[b0bh00d]

The package lacks the ability to watch an entire tree for changes. To address that, I added a Boolean to the system, and the AddDeepWatch() and DeepWatch() functions to enable the 'bWatchSubtree' parameter of ReadDirectoryChanges() with this Boolean. This will allow the watch to report events anywhere within the watched folder tree.

The original functions, AddWatch() and Watch(), continue to behave shallow as they did before--only watching the specified folder--so existing code will not be impacted.

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This PR (HEAD: 1305fe561f77c056d8f2d30112c0913c4f350430) has been imported to Gerrit for code review.

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