Rubber Stamped by Mark Rowe (originally reviewed by Sam Weinig).

        (Reintroducing patch added in r44492, and reverted in r44796.)

        Change the implementation of op_throw so the stub function always modifies its
        return address - if it doesn't find a 'catch' it will switch to a trampoline
        to force a return from JIT execution.  This saves memory, by avoiding the need
        for a unique return for every op_throw.

        * jit/JITOpcodes.cpp:
        (JSC::JIT::emit_op_throw):
            JITStubs::cti_op_throw now always changes its return address,
            remove return code generated after the stub call (this is now
            handled by ctiOpThrowNotCaught).
        * jit/JITStubs.cpp:
        (JSC::):
            Add ctiOpThrowNotCaught definitions.
        (JSC::JITStubs::DEFINE_STUB_FUNCTION):
            Change cti_op_throw to always change its return address.
        * jit/JITStubs.h:
            Add ctiOpThrowNotCaught declaration.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@44838 268f45cc-cd09-0410-ab3c-d52691b4dbfc