Keep clang Address Sanitizer happy

Allocating 15 bytes with the 8-byte aligned memory at offset 8 of
15, would overflow the buffer, which would be fairly likely to
have no effect. But ASan notices this if you run it on AVX hardware,
unlike the Jenkins build which runs on SSE4.1. The good news is
that this fix is enough to make all the existing tests pass under
ASan on AVX.

Change-Id: I61ff11687709e096c70a162d3514227cb243561d
Merge release-4-6 into master

Conflicts (only Copyright header):
	src/gromacs/mdlib/nbnxn_kernels/simd_4xn/nbnxn_kernel_simd_4xn_outer.h

Change-Id: I0c9b713d95343c13fa6e3154b8d08a9ca43e7363
Merge "Merge release-4-6 into master"