Fix the build with GCC 4.8
https://bugs.webkit.org/show_bug.cgi?id=113147

Reviewed by Allan Sandfeld Jensen.

Source/JavaScriptCore:

Initialize JSObject* exception to suppress warnings that make
the build fail because of -Werror=maybe-uninitialized.

* runtime/Executable.cpp:
(JSC::FunctionExecutable::compileForCallInternal):
(JSC::FunctionExecutable::compileForConstructInternal):

Source/WTF:

Disable diagnostic warning -Wunused-local-typedefs for GCC 4.8
since dummy typedefs are commonly used in the codebase.

* wtf/Compiler.h:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@147640 268f45cc-cd09-0410-ab3c-d52691b4dbfc