DFG JIT should be able to compile op_throw

DFG JIT should be able to compile op_throw
https://bugs.webkit.org/show_bug.cgi?id=68571

Reviewed by Geoffrey Garen.

This compiles op_throw in the simplest way possible: it's an OSR
point back to the old JIT. This is a good step towards increasing
coverage, particularly on Kraken, but it's neutral because the
same functions that do throw also use some other unsupported
opcodes.

* dfg/DFGByteCodeParser.cpp:
(JSC::DFG::ByteCodeParser::parseBlock):
* dfg/DFGCapabilities.h:
(JSC::DFG::canCompileOpcode):
* dfg/DFGNode.h:
* dfg/DFGPropagator.cpp:
(JSC::DFG::Propagator::propagateNodePredictions):
* dfg/DFGSpeculativeJIT.cpp:
(JSC::DFG::SpeculativeJIT::compile):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@95683 268f45cc-cd09-0410-ab3c-d52691b4dbfc