Cascade detection of SSE3 support and up

If SSE2 isn't supported, then SSE3 can't be either. Onwards and upwards
for SSSE3, SSE4.1, SSE4.2 and AVX. The test for AVX2 was already there.

(cherry-picked with modification from qtbase commit
a071ba629b89dbbe458d0865a0c4ebc3f92d3524; modified because Qt 4 checks
for SSE and MMX)

Task-number: QTBUG-24773
Change-Id: I005258db52d8abcd407a99b8ebcc23cdea8e3d9f
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>