auto merge of #19439 : nodakai/rust/liblibc-getsid, r=acrichto

```
#include <unistd.h>

pid_t getsid(pid_t pid);

CONFORMING TO
       SVr4, POSIX.1-2001.
```
debuginfo: Fix multi-byte character related bug in cleanup scope handling.

Also see issue #18791.
Pop on binary heaps does not have constant time complexity.

pop calls siftdown, siftdown calls siftdown_range, and siftdown_range
loops on an index that can start as low as 0 and approximately doubles
each iteration.
auto merge of #19450 : jbapple/rust/pq-pop-time, r=Gankro

pop calls siftdown, siftdown calls siftdown_range, and siftdown_range
loops on an index that can start as low as 0 and approximately doubles
each iteration.
rustdoc: Check for href when prepending rootPath

Fixes #18354.
auto merge of #19427 : scialex/rust/doc-attr-macros, r=sfackler

this allows one to, for example, use #[doc = $macro_var ] in macros.
auto merge of #19357 : michaelwoerister/rust/fix-issue-18791, r=alexcrichton

One negative side-effect of this change is that there might be quite a bit of copying strings out of the codemap, i.e. one copy for every block that gets translated, just for taking a look at the last character of the block. If this turns out to cause a performance problem then `CodeMap::span_to_snippet()` could be changed return `Option<&str>` instead of `Option<String>`.

Fixes #18791
auto merge of #19443 : nodakai/rust/another-missing-extracflags, r=alexcrichton

rust-lang/rust@102b1a5bf1a60eeafb752844e5c98fe5f4e3b992 was not enough!
better wording
remove two unneccesary directories from configure
replace 'but' with 'and'
auto merge of #19460 : steveklabnik/rust/conf_fixes, r=alexcrichton
Improve documentation of checked_* functions
Update comment to current file path for intrinsics
lldb: Fix pretty printer for nullable-opt enums with fat pointers.
gdb: Fix pretty printer for nullable-opt enums with fat pointers.
libcore: add `Rhs` input parameter to comparison traits
Test PartialEq multidispatch
Treat builtin bounds like all other kinds of trait matches. Introduce a simple hashset in the fulfillment context to catch cases where we register the exact same obligation twice. This helps prevent duplicate error reports but also handles the recursive obligations created by builtin bounds.
Correct various compile-fail tests. Most of the changes are because we
now don't print duplicate errors within one context, so I sometimes
had to break functions into two functions.