Update to ASM 4.1

With ASM 4.1 implicit initial frames are no longer processed as events.
This required a rework and simplification of the frame processing logic.
diff --git a/org.jacoco.doc/docroot/doc/changes.html b/org.jacoco.doc/docroot/doc/changes.html
index cdde19b..8557fa5 100644
--- a/org.jacoco.doc/docroot/doc/changes.html
+++ b/org.jacoco.doc/docroot/doc/changes.html
@@ -20,6 +20,11 @@
 
 <h2>Trunk Build @qualified.bundle.version@ (@build.date@)</h2>
 
+<h3>Non-functional Changes</h3>
+<ul>
+  <li>Upgrade to ASM 4.1 (GitHub #37)</li>
+</ul>
+
 <h2>Release 0.6.0 (2012/10/06)</h2>
 
 <h3>New Features</h3>