God. Damnit. Isaac.

This reverts commit d995ef12

-> Made API and tests use `transmute` for f64/u64 instead of `as`
-> Changed relevant logical shifts to (correctly) be arithmetic shifts
-> Fixed small typo in tests
-> (misc) Made STORE correctly handle arbitrary (< 64) sized ints

Note that these currently fail because I am not doing the bitwise
f64/u64 conversion correctly. This should be done either via
from_bits/to_bits (unstable) or std::mem::transmute (unsafe).

python tests: use $MU_ZEBU if it is defined as the project directory, otherwise use default path tracing from the file itself

This is mostly in service of implementing TagRef64, which can
now be initialized by a bundle (but is as of yet not properly
implemented).

this will fix the test case

Merge Aarch64 into develop

See merge request !11