Assign FIXMEs to me and remove obsolete ones

Also fixed capitalization of documentation

Author: fee1-dead

alloc/tests/const_fns.rs

@@ -10,7 +10,7 @@ pub const MY_VEC: Vec<usize> = Vec::new();
 #[allow(dead_code)]
 pub const MY_STRING: String = String::new();
 
-// FIXME remove this struct once we put `K: ?const Ord` on BTreeMap::new.
+// FIXME(fee1-dead) remove this struct once we put `K: ?const Ord` on BTreeMap::new.
 #[derive(PartialEq, Eq, PartialOrd)]
 pub struct MyType;
 

alloc/tests/lib.rs

@@ -25,8 +25,6 @@
 #![feature(string_remove_matches)]
 #![feature(const_btree_new)]
 #![feature(const_trait_impl)]
-// FIXME remove this when const_trait_impl is not incomplete anymore
-#![allow(incomplete_features)]
 
 use std::collections::hash_map::DefaultHasher;
 use std::hash::{Hash, Hasher};