-changes in gitignore

-changed "absent" to "excluded" everywhere
-added Events support:
 *systems are scanned by handleEvent() function
 *generate system callers for events
 *event sending have (untested) multithreaded support
 *EventInput structure in System has input components for event

.gitignore

@@ -1,17 +1,5 @@
-dub.userprefs
-dub.selections.json
-.dub
-/.vscode
-LOC
-perf.data
-perf.data.old
-*.o
-*.a
-*.obj
-*.exe
-*.lib
-*.so
-*.def
-*.lib
-*.dll
-*.exp
+*
+!source
+!tests
+!dub.json
+!.gitignore