DFG 32-bit support for op_call and op_construct causes

DFG 32-bit support for op_call and op_construct causes
run-javascriptcore-tests to fail
https://bugs.webkit.org/show_bug.cgi?id=69171

Reviewed by Gavin Barraclough.

This fixes one obvious bug that was causing test failures (no
support for dummy slow case for op_add in 32_64), and disables
op_call and op_construct by default.

* dfg/DFGCapabilities.h:
(JSC::DFG::canCompileOpcode):
* jit/JITArithmetic32_64.cpp:
(JSC::JIT::emit_op_add):
(JSC::JIT::emitSlow_op_add):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@96429 268f45cc-cd09-0410-ab3c-d52691b4dbfc