Fix a bug in exporting trait implementations

I used the wrong condition where I was looking for "is this method public or is
this implementation a trait" rather than what was being checked.
Improve various Vim syntax highlighting things.

- Implement comment nesting (the implementation is quite ugly at present
  and is not quite correct; note the big comment in that area).

- Highlight invalid escape sequences as errors.

- Fix up various inconsistencies and incorrectnesses in number
  highlighting.

- Update prelude items (``std::io::{Buffer, Writer, Reader, Seek}``).

- Highlight the ``proc`` keyword.

- Remove %-formatting sequence highlighting (a relic of old formatting).

- Don't highlight TODO in strings (it's unconventional).
Don't infinitely recurse in a process test

Note entirely sure how this is passing at all today, but regardless this fixes
the problems seen in #10790
Move std::util::ignore to std::prelude::drop

It's a more fitting name for the most common use case of this function.
auto merge of #10783 : sfackler/rust/drop, r=alexcrichton

It's a more fitting name for the most common use case of this function.
std::str: remove from_utf8.

This function had type &[u8] -> ~str, i.e. it allocates a string
internally, even though the non-allocating version that take &[u8] ->
&str and ~[u8] -> ~str are all that is necessary in most circumstances.
std::str: s/from_utf8_slice/from_utf8/, to make the basic case shorter.
auto merge of #10793 : chris-morgan/rust/2013-12-04-vim-updates, r=Aatch

- Implement comment nesting (the implementation is quite ugly at present
  and is not quite correct; note the big comment in that area).

- Highlight invalid escape sequences as errors.

- Fix up various inconsistencies and incorrectnesses in number
  highlighting.

- Update prelude items (``std::io::{Buffer, Writer, Reader, Seek}``).

- Highlight the ``proc`` keyword.

- Remove %-formatting sequence highlighting (a relic of old formatting).

- Don't highlight TODO in strings (it's unconventional).
auto merge of #10794 : alexcrichton/rust/issue-10790, r=alexcrichton

Note entirely sure how this is passing at all today, but regardless this fixes
the problems seen in #10790 

Closes #10790
auto merge of #10788 : alexcrichton/rust/fixes, r=pcwalton

I used the wrong condition where I was looking for "is this method public or is
this implementation a trait" rather than what was being checked.
auto merge of #10701 : huonw/rust/rm-from_utf8, r=brson

This function had type &[u8] -> ~str, i.e. it allocates a string
internally, even though the non-allocating version that take &[u8] ->
&str and ~[u8] -> ~str are all that is necessary in most circumstances.
Add Json example and documentation.
pass make check
correct typing error
correct code '''