[AArch64] Add alternative division and sqrt methods

With this patch, alternative division and sqrt can be chosen by specifying -DENABLE_ALTDIV=TRUE -DENABLE_ALTSQRT=TRUE as cmake options.
The alternative methods use combinations of FMA operations to compute division and sqrt.
These methods could possibly be beneficial for micro-architectures on which the corresponding instructions are non-pipelined and have long latencies.

Co-authored-by: shibatch <shibatch.sf.net@gmail.com>