Convert more tests over to the new atomic instructions.

I did not convert Atomics-32.ll and Atomics-64.ll by hand; the diff is autoupgrade output.

The wmb test is gone because there isn't any way to express wmb with the new atomic instructions; if someone really needs a non-asm way to write a wmb on Alpha, a platform-specific intrisic could be added.

llvm-svn: 140566