[Mac] Added comment to explain ugly code.

mac/KeymanEngine4Mac/KeymanEngine4Mac/KME/OnScreenKeyboard/KeyView.m

@@ -232,6 +232,12 @@ const NSTimeInterval repeatInterval = 0.05f;
 }
 
 -(void)processKeyClick {
+    // This code was previously incorrectly implemented because the function call failed to pass "self" as the
+    // final parameter. This page describes the fix, as implemented here:
+    // https://stackoverflow.com/questions/27626617/how-to-solve-performselector-may-cause-leak-because-its-selector-is-unknown?noredirect=1&lq=1
+    // This is almost certainly not the *best* way to implement this, but we're up against our release deadline,
+    // so it should be revisted soon to come up with a more readable and reliable approach, and maybe even a
+    // unit-testable one.
     SEL selector = self.action;
     IMP imp = [self.target methodForSelector:selector];
     void (*func)(id, SEL, id) = (void *)imp;