Several fixes for DragonFly (rebase)
load_self() needs to be public
Implement `reserve_len` and `reserve_len_exact` for VecMap
debuginfo: Create debuginfo for for-loop variables again.
debuginfo: Clean the debuginfo module up a bit.
debuginfo: Add test case for destructured for-loop variable.
Support all variants of WherePredicate

Adds support for all variants of ast::WherePredicate in clean/mod.rs. Fixes #20048, but will need modification when EqualityPredicates are fully implemented in #20041.
rustdoc: unmarked code fences are doctests too
Address code review nits
clean up `BinaryHeap` code
rustdoc: render `for<>` on old closure lifetimes
rustdoc: render higher-rank trait bounds

Fix #19915
rustdoc: Use unboxed closure sugar

This unfortunately leaves sugaring Fn/FnMut/FnOnce on cross-crate
re-exports for future work.

cc #19909
rustdoc: Use Fn trait sugar for external paths

Fix #19909
Rename to_ascii_{lower,upper} to to_ascii_{lower,upper}case, per #14401

[breaking-change]
auto merge of #19934 : tomjakubowski/rust/rustdoc-unboxed-closures-redux, r=alexcrichton

We render HRTB and the unboxed closure trait sugar (the so-called 
"parenthesized" notation) where appropriate. Also address the new
`for` syntax on the old closures.
mk: Build jemalloc with -ffunction-sections

It's quite possible that small programs don't use all of jemalloc, and building
with -ffunction-sections and -fdata-sections allows the linker (via
--gc-sections) to strip out all unused code at link time. This decreases the
size of a "hello world" executable for me from 716K to 482K with no measurable
impact on link time. After this patch jemalloc is still the largest portion of
our hello world executables, but this helps cut down on the size at least
somewhat!
auto merge of #20024 : mneumann/rust/dragonfly-fixes3, r=alexcrichton
Remove Ascii, AsciiCast, OwnedAsciiCast, AsciiStr, IntoBytes, IntoString.

As a replacement, add is_ascii() to AsciiExt, and implement AsciiExt for u8 and char.

[breaking-change]
std::ascii: Use u8 methods rather than the maps directly.