per method and list of def-ids per trait.

This reverts commit a8f039a0.

Changes:

- Refactor move mode computation
- Removes move mode arguments, unary move, capture clauses
  (though they still parse for backwards compatibility)
- Simplify how moves are handled in trans
- Fix a number of illegal copies that cropped up
- Workaround for bug involving def-ids in params
  (see details below)

Future work (I'll open bugs for these...):

- Improve error messages for moves that are due
  to bindings
- Add support for moving owned content like a.b.c
  to borrow check, test in trans (but I think it'll
  "just work")
- Proper fix for def-ids in params

Def ids in params:

Move captures into a map instead of recomputing.

This is a workaround for a larger bug having to do with the def-ids associated
with ty_params, which are not always properly preserved when inlining.  I am
not sure of my preferred fix for the larger bug yet.  This current fix removes
the only code in trans that I know of which relies on ty_param def-ids, but
feels fragile.

r=pcwalton

~20% perf win for trans on -O0, with other minor improvements across the board.
No effect on -O2.

librustc: Encode language items into a special lookup table. 9% improvement in hello world compile time.

and rename "class" to "struct" everywhere possible (except local
vars, I was too lazy for that) -- that is why this commit is so
big.

No review, just dead code removal and renaming.

Closes #3515

This is part of the transition to "@int as @Trait".

Fixes #3261
Fixes #3443

rustc: Check self types in method lookup; allow required trait methods to have self types; write self types into metadata

so that the "list metadata" command doesn't print out anything
about intrinsics, but other code can see them.

Closes #2771

This reverts commit 7ef825bb.

18s perf regression compiling rustc with opts

This reverts commit 7f6ee0ce.

cc #2540

Fixed up a few FIXMEs in lib/llvm to use more descriptive data
types. Covered FIXMEs in metadata::{creader, csearch, decoder} and
one in encoder.