[APInt] Add rvalue reference support to and, or, xor operations to allow their...

[APInt] Add rvalue reference support to and, or, xor operations to allow their memory allocation to be reused when possible

This extends an earlier change that did similar for add and sub operations.

With this first patch we lose the fastpath for the single word case as operator&= and friends don't support it. This can be added there if we think that's important.

I had to change some functions in the APInt class since the operator overloads were moved out of the class and can't be used inside the class now. The getBitsSet change collides with another outstanding patch to implement it with setBits. But I didn't want to make this patch dependent on that series.

I've also removed the Or, And, Xor functions which were rarely or never used. I already commited two changes to remove the only uses of Or that existed.

Differential Revision: https://reviews.llvm.org/D30612

llvm-svn: 297121