builtins: relax __iso_volatile_{load,store}32

This is reduced from MSVC's MSVCPRT 14.21.27702 atomic header.  Because
Windows is a LLP64 environment, `long`, `long int`, and `int` are all
synonymous.  Change the signature for `__iso_volatile_load32` and
`__iso_volatile_store32` to accept a `long int` instead.  This allows
an implicit cast of `int` to `long int` while also permitting `long`
to be accepted.

llvm-svn: 364137