ART: Changes to try-catch in GraphBuilder

This patch adds an additional case into the insertion algorithm for
HTryBoundary inside HGraphBuilder in order to better handle catch
blocks covered by a TryItem.

Building SSA form also required to stop combining HTryBoundaries for
neighbouring TryItems because it was not clear which exception
handlers belong to which try block.

Change-Id: Ic68bd6ef98fee784609fa593cb08dca1f00a15e0
diff --git a/compiler/optimizing/nodes.cc b/compiler/optimizing/nodes.cc
index 881f9ec..b82e37c 100644
--- a/compiler/optimizing/nodes.cc
+++ b/compiler/optimizing/nodes.cc
@@ -1050,6 +1050,7 @@
   successors_.Reset();
   AddSuccessor(new_block);
 
+  GetGraph()->AddBlock(new_block);
   return new_block;
 }