remove confusing intermediate 'where' in evaluate_assignment()

In evaluate_assignment(), a local variable (named 'where') contains
the input expression (named 'expr', like in most other functions).
This is doubly confusing because:
*) both variables hold the same pointer.
*) the name 'where' is normally used for a string with extra
   information for error messages.

So, remove this intermediate var and use the original 'expr' instead.

Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
1 file changed