Fix bug and refactor optimized try-catch.

Fix bug and refactor optimized try-catch.

 When untagged values flow into a exception-throwing instruction
 they need to be converted eagerly. Catch block entries assume all
 values are tagged at the entry.

 I changed the generation of moves at throwing
 instructions in try-catch: Instead of manuallu emitting moves,
 construct a parallel move and use the resolver to emit the native code.
 This eliminates a lot of duplicated code from all platforms.

 It will also allow to re-use stack space that is currently allocated
 separately for each individual try-catch in a function.

 I added a few more unrelated minor changes in various parts of the VM
 * Simpilify guard code generation
 * Resolve refactoring TODO in deoptimization
 * Improve names

R=johnmccutchan@google.com

Committed: https://code.google.com/p/dart/source/detail?r=31536

[Florian Schneider, 2014-01-06 15:12:50]

This is relanding r31326 plus a bug fix in optimized try-catch uncovered by it.

https://codereview.chromium.org/125103002/diff/1/runtime/vm/flow_graph_compil...
File runtime/vm/flow_graph_compiler.cc (right):

https://codereview.chromium.org/125103002/diff/1/runtime/vm/flow_graph_compil...
runtime/vm/flow_graph_compiler.cc:334: ASSERT(!src.IsDoubleStackSlot());
I added these two asserts that were violated before.

[Cutch, 2014-01-06 18:55:22]

lgtm

[Florian Schneider, 2014-01-07 09:58:57]

Committed patchset #2 manually as r31536 (presubmit successful).