Reviewed by Oliver Hunt.

        Do not have two different asCell APIs in JSValue
        https://bugs.webkit.org/show_bug.cgi?id=47979

        Remove JSCell* asCell(JSValue) in favor of only using
        JSValue::asCell().

        * API/APICast.h:
        (toRef):
        * jit/JITPropertyAccess32_64.cpp:
        (JSC::JIT::testPrototype):
        * jit/JITStubs.cpp:
        (JSC::JITThunks::tryCachePutByID):
        (JSC::JITThunks::tryCacheGetByID):
        (JSC::DEFINE_STUB_FUNCTION):
        * runtime/GetterSetter.h:
        (JSC::asGetterSetter):
        * runtime/JSByteArray.h:
        (JSC::asByteArray):
        * runtime/JSCell.h:
        (JSC::JSCell::getCallData):
        (JSC::JSCell::getConstructData):
        * runtime/JSString.h:
        (JSC::RopeBuilder::appendValueInConstructAndIncrementLength):
        (JSC::asString):
        * runtime/JSValue.h:
        * runtime/Operations.cpp:
        (JSC::jsIsObjectType):
        * runtime/Operations.h:
        (JSC::normalizePrototypeChain):
        * runtime/Protect.h:
        (JSC::gcProtect):
        (JSC::gcUnprotect):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@70749 268f45cc-cd09-0410-ab3c-d52691b4dbfc