Implement inotify based directory watcher.

tests/0-dirwatcher.d

@@ -0,0 +1,66 @@
+/++ dub.sdl:
+	name "test"
+	dependency "eventcore" path=".."
++/
+module test;
+
+import eventcore.core;
+import std.stdio : File, writefln;
+import std.file : exists, remove;
+import core.time : msecs;
+
+bool s_done;
+int s_cnt = 0;
+
+enum testFilename = "test.dat";
+
+void main()
+{
+	if (exists(testFilename))
+		remove(testFilename);
+
+	auto id = eventDriver.watchers.watchDirectory(".", false, (id, ref change) {
+		switch (s_cnt++) {
+			default: assert(false);
+			case 0:
+				assert(change.kind == FileChangeKind.added);
+				assert(change.directory == ".");
+				assert(change.name == testFilename);
+				break;
+			case 1:
+				assert(change.kind == FileChangeKind.modified);
+				assert(change.directory == ".");
+				assert(change.name == testFilename);
+				break;
+			case 2:
+				assert(change.kind == FileChangeKind.removed);
+				assert(change.directory == ".");
+				assert(change.name == testFilename);
+				s_done = true;
+				eventDriver.core.exit();
+				break;
+		}
+	});
+
+	auto fil = File(testFilename, "wt");
+
+	auto tm = eventDriver.timers.create();
+	eventDriver.timers.set(tm, 100.msecs);
+	eventDriver.timers.wait(tm, (tm) {
+		scope (failure) assert(false);
+		fil.write("test");
+		fil.close();
+		eventDriver.timers.set(tm, 100.msecs);
+		eventDriver.timers.wait(tm, (tm) {
+			scope (failure) assert(false);
+			remove(testFilename);
+		});
+	});
+
+	ExitReason er;
+	do er = eventDriver.core.processEvents();
+	while (er == ExitReason.idle);
+	//assert(er == ExitReason.outOfWaiters); // FIXME: see above
+	assert(s_done);
+	s_done = false;
+}