[patch, libfortran] Speed up cshift for dim > 1

[Thomas Koenig]

Hi Jerry,

> OK for trunk.

Committed as r249350.

Thanks for the review, and thanks to Dominique for testing.

Doing the same for eoshift should be straightforward, I'll do
that later (but certainly before the 8.1 release).

Next, on to cshift with an array as shift.  I have some ideas
there, let's see how that works out.

Regards

	Thomas