findRoot optimization and bugfix

and minor std.math cleanup
Agreed. It's not only that the switching is (horrendously) slow. Even if you just use the SSE units with single scalars, they tend to be faster than the `real` equivalent, sometimes by quite a lot. x87 is basically deprecated from a processor company's point of view. It probably won't be going away for quite a while still, given that x86 is all about backwards compatibility, but I won't be surprised if it is entirely implemented in microcode soon.

Remember that perlin noise microbenchmark that was discussed on the NG a while ago? Our abysmal performance there (several times slower than C++) was caused by exactly this issue.