* store immediate values as int64_t, not int. come on, we should be happy

* store immediate values as int64_t, not int. come on, we should be happy
when there are immediates, let's not worry about the memory overhead of
this :)

* add addU64Imm(uint64_t val) to machineinstrbuilder

(seriously: this seems required to support 64-bit immediates cleanly. if it
_really_ gets on your nerves, feel free to pull it out ;) )

coming up next week: "all your floating point constants are belong to us"

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@21208 91177308-0d34-0410-b5e6-96231b3b80d8