doc: remove node.js dependency

`prep.js` outputs its own HTML directives, which `pandoc` cannot
recognize when converting the document into LaTeX (this is why the
PDF docs have never been highlighted as of now).

Note that if we were to add the `.rust` class to snippets, we could
probably use pandoc's native highlighting capatibilities i.e. Kate.
doc: have a real switch b/w LaTeX compilers
doc: CSS fixes

- fixup and refactor highlighting code
- have a proper print stylesheet
doc: auto-generate LaTeX includes
doc: remove outdated tutorial entry, restore removed Makefile entries
auto merge of #12783 : adrientetar/rust/more-docs, r=alexcrichton

- remove `node.js` dep., it has no effect as of #12747 (1)
- switch between LaTeX compilers, some cleanups
- CSS: fixup the print stylesheet, refactor highlighting code (2)

(1): `prep.js` outputs its own HTML directives, which `pandoc` cannot recognize when converting the document into LaTeX (this is why the PDF docs have never been highlighted as of now).

Note that if we were to add the `.rust` class to snippets, we could probably use pandoc's native highlighting capatibilities i.e. Kate ([here is](http://adrientetar.github.io/rust-tuts/tutorial/tutorial.pdf) an example of that).

(2): the only real highlighting change is for lifetimes which are now brown instead of red, the rest is just refactor of twos shades of red that look the same.
Also I made numbers highlighting for src in rustdoc a tint more clear so that it is less bothering.

@alexcrichton, @huonw

Closes #9873. Closes #12788.
Add basic backtrace functionality

Whenever a failure happens, if a program is run with
`RUST_LOG=std::rt::backtrace` a backtrace will be printed to the task's stderr
handle. Stack traces are uncondtionally printed on double-failure and
rtabort!().

This ended up having a nontrivial implementation, and here's some highlights of
it:

* We're bundling libbacktrace for everything but OSX and Windows
* We use libgcc_s and its libunwind apis to get a backtrace of instruction
  pointers
* On OSX we use dladdr() to go from an instruction pointer to a symbol
* On unix that isn't OSX, we use libbacktrace to get symbols
* Windows, as usual, has an entirely separate implementation

Lots more fun details and comments can be found in the source itself.

Closes #10128