Improved message when sse2 code can't compile.
Improved message when sse2 code can't compile.

(as a side note, the stock gcc (4.2.1) on OpenBSD 4.9 miscompiles the
sse2 test case and produces the following gibberish:

    psrlq   $0x11000000000000002a, %xmm0

gcc 4.2.4 does not have this problem)

git-svn-id: 64df4a12fe8ab3fee7db88f0f615ae26a3770e3d@953 3eaf19af-ecc0-40f6-b43f-672aa0c71c71

mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs