extra: store values for expressions like "foo[3].bar"

extra: store values for expressions like "foo[3].bar"

Before we used to store values for array elements like:

	foo[3] = x;

But we didn't for:

	foo[3].bar = y;

The reason is that foo[3].bar isn't an array so is_array() returned false,
but it does contain an array so the normal code wouldn't store it either.
I've added a work-around.  It's not ideal...

Also I had to change smatch_flow.c because it wasn't using the right
functions to see if there was an extra state.  The original smatch_flow
code couldn't handle chunk values.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>