Remove (lots of) dead code

Found with https://github.com/est31/warnalyzer.

Dubious changes:
- Is anyone else using rustc_apfloat? I feel weird completely deleting
  x87 support.
- Maybe some of the dead code in rustc_data_structures, in case someone
  wants to use it in the future?
- Don't change rustc_serialize

  I plan to scrap most of the json module in the near future (see
  https://github.com/rust-lang/compiler-team/issues/418) and fixing the
  tests needed more work than I expected.

TODO: check if any of the comments on the deleted code should be kept.

compiler/rustc_mir/src/interpret/eval_context.rs

@@ -226,16 +226,6 @@ impl<'mir, 'tcx, Tag> Frame<'mir, 'tcx, Tag> {
 }
 
 impl<'mir, 'tcx, Tag, Extra> Frame<'mir, 'tcx, Tag, Extra> {
-    /// Get the current location within the Frame.
-    ///
-    /// If this is `Err`, we are not currently executing any particular statement in
-    /// this frame (can happen e.g. during frame initialization, and during unwinding on
-    /// frames without cleanup code).
-    /// We basically abuse `Result` as `Either`.
-    pub fn current_loc(&self) -> Result<mir::Location, Span> {
-        self.loc
-    }
-
     /// Return the `SourceInfo` of the current instruction.
     pub fn current_source_info(&self) -> Option<&mir::SourceInfo> {
         self.loc.ok().map(|loc| self.body.source_info(loc))
@@ -459,11 +449,6 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         ty.size.truncate(value)
     }
 
-    #[inline]
-    pub fn type_is_sized(&self, ty: Ty<'tcx>) -> bool {
-        ty.is_sized(self.tcx, self.param_env)
-    }
-
     #[inline]
     pub fn type_is_freeze(&self, ty: Ty<'tcx>) -> bool {
         ty.is_freeze(self.tcx, self.param_env)