SIMDWrapper should not provide an operator==

Or at least, it should not be implemented as a plain ==, as any usage of it would lead to a "comparing floating-point with '==' or '!=' is unsafe" warning if we activate -Wfloat, which we should.

Dropping the definition of this operator breaks a number of things, but it seems to be essentially tests and they should be fixed to do proper comparisons, as they are not reliable as is.