Reviewed by Maciej.

        Make code generation not use a temporary for the left-hand side of an
        expression if the right-hand side is a local variable.

        * VM/CodeGenerator.cpp:
        (KJS::CodeGenerator::isLocal):
        * VM/CodeGenerator.h:
        (KJS::CodeGenerator::leftHandSideNeedsCopy):
        (KJS::CodeGenerator::emitNodeForLeftHandSide):
        * kjs/nodes.cpp:
        (KJS::ResolveNode::isPure):
        (KJS::BracketAccessorNode::emitCode):
        (KJS::AddNode::emitCode):
        (KJS::SubNode::emitCode):
        (KJS::ReadModifyResolveNode::emitCode):
        (KJS::AssignDotNode::emitCode):
        (KJS::ReadModifyDotNode::emitCode):
        (KJS::AssignBracketNode::emitCode):
        (KJS::ReadModifyBracketNode::emitCode):
        * kjs/nodes.h:
        (KJS::ExpressionNode::):
        (KJS::BooleanNode::):
        (KJS::NumberNode::):
        (KJS::StringNode::):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@34555 268f45cc-cd09-0410-ab3c-d52691b4dbfc