Yet another improvement for simplified_indexed

[Chris Dams]

Hello everybody,

I discovered that in the function rename_dummy_indices in indexed.cpp.
The line

	for (unsigned i=0; i<global_size; i++)

can be changed to

	for (unsigned i=0; i<local_size; i++)

This makes the result of simplify_indexed more canonical. Reason: if I
have in a sum terms in which two dummy indices occur and I also have terms
in which one dummy index occurs, The terms in which one dummy index occurs
always get the same one by dummy index renaming. This may make terms equal
that would otherwise have been considered not to be equal.

Bye,
Chris Dams