-> 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

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

unwinding

generated code. Now internally Zebu use make_boot_image for
compile_to_sharedlib

macro.

This reverts commit 54ce8e1c.