* Add lifetime constraints on some bignum vops so the register
allocator doesn't overwrite the arguments;
* Tweak error-code finding code in alpha-arch.c; make cosmetic
32->64-bit changes while we're at it (did this ever work?
It doesn't look like it could have.).
Tests now pass up to float.pure.lisp.
Add :CIX-guarded VOPs for integer-length, just for kicks.