Code review snippets to address from @davidben

Also:
* sus_if_msvc for attributes should be sus_if_msvc_not_cl
  * "language is msvc variant" vs "compiler is msvc"
  * sus_if_gnuc_language
* test wrapping for each integer size, esp < 32bit
* not destroy nevervalue? since it's in a union can that be a
  requirement on NeverValueTypes, and is C++ okay with constructing
  an object in a place where one already exists and was not destroyed?

Author: danakj

sus/CMakeLists.txt

@@ -131,7 +131,6 @@ target_sources(subspace PUBLIC
     "iter/zip.h"
     "macros/__private/compiler_bugs.h"
     "macros/assume.h"
-    "macros/arch.h"
     "macros/builtin.h"
     "macros/compiler.h"
     "macros/eval_macro.h"