:art: Use constructors for SinOsc

yet mark the type as non abstract to allow var SinOsc foo and new SinOsc

diff --git a/plug b/plug
index 6a0710d81f9d98f4822ce1fd5d43a54c95768899..3934c8816d07216e707cf4c568d1fbf9e6e8f529 160000 (submodule)
--- a/plug
+++ b/plug
@@ -1 +1 @@
-Subproject commit 6a0710d81f9d98f4822ce1fd5d43a54c95768899
+Subproject commit 3934c8816d07216e707cf4c568d1fbf9e6e8f529