Fix an ICE on a cast from an inferred nil to uint

Fixes #10991.
rustc: Start accepting `*const T`

This does not yet change the compiler and libraries from `*T` to `*const T` as
it will require a snapshot to do so.

cc #7362
rustc: Add self/super hint for extern crate resolve errors.
emacs: Don't overwrite font lock for attributes

This addresses the font lock regression introduced by the earlier pull
request #14818 - attributes are no longer be highligted inside of comments
and strings.

Also add some font lock test infrastructure and some tests for attribute
font locking.
emacs: Add shebang to test script
emacs: Remove outdated references to ~ in tests
rustc: reduce redundant resolve errors.
Wrap debuginfo.rs at 80 columns.

Plus a few other misc style things.
librustc: Don't overwrite vtables when coercing to trait object.
Mark all crates except std as experimental
fix signatures of mmap-related functions from libc
rustdoc: Fix testing indented code blocks

The collapse/unindent passes were run in the wrong order, generating different
markdown for indented tests.
rustdoc: Don't inject `extern crate std`.

No need to duplicate the compiler's work!

Closes #14999
std: Remove dual export of `Show`

Closes #14996
auto merge of #14994 : nick29581/rust/comments, r=bstrie

Plus a few other misc style things.
auto merge of #15000 : alexcrichton/rust/fix-rustdoc-tests, r=huonw

Commits have the descriptions.
auto merge of #14990 : tomjakubowski/rust/emacs-fix-attribute-highlight, r=pnkfelix

This addresses the font lock regression introduced by the earlier pull
request #14818 - attributes are no longer be highligted inside of comments
and strings.

Also add some font lock test infrastructure and some tests for attribute
font locking and fix some minor nits.
auto merge of #14984 : thestinger/rust/libc, r=alexcrichton
Bug fixes for flowgraph construction.

1. After recursively processing an ExprWhile, need to pop loop_scopes
   the same way we do for ExprLoop.

2. Proposed fix for flowgraph handling of ExprInlineAsm: we need to
   represent the flow into the subexpressions of an `asm!` block.
NodeIndex should derive `Show`.