std: Stabilize APIs for the 1.8 release

This commit is the result of the FCPs ending for the 1.8 release cycle for both
the libs and the lang suteams. The full list of changes are:

Stabilized

* `braced_empty_structs`
* `augmented_assignments`
* `str::encode_utf16` - renamed from `utf16_units`
* `str::EncodeUtf16` - renamed from `Utf16Units`
* `Ref::map`
* `RefMut::map`
* `ptr::drop_in_place`
* `time::Instant`
* `time::SystemTime`
* `{Instant,SystemTime}::now`
* `{Instant,SystemTime}::duration_since` - renamed from `duration_from_earlier`
* `{Instant,SystemTime}::elapsed`
* Various `Add`/`Sub` impls for `Time` and `SystemTime`
* `SystemTimeError`
* `SystemTimeError::duration`
* Various impls for `SystemTimeError`
* `UNIX_EPOCH`
* `ops::{Add,Sub,Mul,Div,Rem,BitAnd,BitOr,BitXor,Shl,Shr}Assign`

Deprecated

* Scoped TLS (the `scoped_thread_local!` macro)
* `Ref::filter_map`
* `RefMut::filter_map`
* `RwLockReadGuard::map`
* `RwLockWriteGuard::map`
* `Condvar::wait_timeout_with`

Closes #27714
Closes #27715
Closes #27746
Closes #27748
Closes #27908
Closes #29866

src/libsyntax/feature_gate.rs

@@ -213,10 +213,10 @@ const KNOWN_FEATURES: &'static [(&'static str, &'static str, Option<u32>, Status
     ("unwind_attributes", "1.4.0", None, Active),
 
     // allow empty structs and enum variants with braces
-    ("braced_empty_structs", "1.5.0", Some(29720), Active),
+    ("braced_empty_structs", "1.5.0", Some(29720), Accepted),
 
     // allow overloading augmented assignment operations like `a += b`
-    ("augmented_assignments", "1.5.0", Some(28235), Active),
+    ("augmented_assignments", "1.5.0", Some(28235), Accepted),
 
     // allow `#[no_debug]`
     ("no_debug", "1.5.0", Some(29721), Active),
@@ -563,8 +563,6 @@ pub struct Features {
     pub cfg_target_feature: bool,
     pub cfg_target_vendor: bool,
     pub cfg_target_thread_local: bool,
-    pub augmented_assignments: bool,
-    pub braced_empty_structs: bool,
     pub staged_api: bool,
     pub stmt_expr_attributes: bool,
     pub deprecated: bool,
@@ -597,8 +595,6 @@ impl Features {
             cfg_target_feature: false,
             cfg_target_vendor: false,
             cfg_target_thread_local: false,
-            augmented_assignments: false,
-            braced_empty_structs: false,
             staged_api: false,
             stmt_expr_attributes: false,
             deprecated: false,
@@ -956,10 +952,7 @@ impl<'a, 'v> Visitor<'v> for PostExpansionVisitor<'a> {
     fn visit_variant_data(&mut self, s: &'v ast::VariantData, _: ast::Ident,
                         _: &'v ast::Generics, _: ast::NodeId, span: Span) {
         if s.fields().is_empty() {
-            if s.is_struct() {
-                self.gate_feature("braced_empty_structs", span,
-                                  "empty structs and enum variants with braces are unstable");
-            } else if s.is_tuple() {
+            if s.is_tuple() {
                 self.context.span_handler.struct_span_err(span, "empty tuple structs and enum \
                                                                  variants are not allowed, use \
                                                                  unit structs and enum variants \
@@ -1196,8 +1189,6 @@ fn check_crate_inner<F>(cm: &CodeMap, span_handler: &Handler,
         cfg_target_feature: cx.has_feature("cfg_target_feature"),
         cfg_target_vendor: cx.has_feature("cfg_target_vendor"),
         cfg_target_thread_local: cx.has_feature("cfg_target_thread_local"),
-        augmented_assignments: cx.has_feature("augmented_assignments"),
-        braced_empty_structs: cx.has_feature("braced_empty_structs"),
         staged_api: cx.has_feature("staged_api"),
         stmt_expr_attributes: cx.has_feature("stmt_expr_attributes"),
         deprecated: cx.has_feature("deprecated"),