Revised the "XOR of yespower" tests to trigger duplicate index in the last

SMix2 invocation in yespower 0.5 for N=2048 with at least one of the values of
r being tested.  This is needed to test that a non-save version of BlockMix is
used in that special case, which would previously be left untested.

CVS-ID: TESTS-OK 1.2
CVS-ID: tests.c 1.2