Do not push a redundant value context in crankshaft.

Do not push a redundant value context in crankshaft.

When visiting AND/OR nodes in a value context during Hydrogren graph generation,
there is no need to push a new value context, the full code generator doesn't do
it, either. While technically it doesn't hurt to do so, this change makes the
context stacks for the full code generator and crankshaft more similar, which
helps comparing the dynamic behaviour of these generators tremendously.

[Sven Panne, 2011-05-26 07:18:46]

The right fix seems to be adding value contexts in the full code generator, not
removing context in crankshaft, so I'll close this issue.