rt: don't save and restore xmm/regs in __morestack.
Feed enum field offsets to type vistors.
Export adt::trans_get_discr abstractly to the type visitor.
When repr'ing an enum value, assert that it matched some variant.
Make the enum visit callback generator more readable
Make intrinsic::Opaque more opaque
Add debug info for boxes
Add debug info for vectors
Add debug info for bare_fn type
Prevent debug info generation of zero-span nodes

If a node has a (0, 0) span, it was not in the source, so debug symbols should not be generated for it.
Add debug info test for boxes
Add debug info test for vectors
add rustdoc comments with examples for the string versions of to_base64 and from_base64
rustpkg: Factor out tests; use a condition instead of returning an option

Pulled out tests into their own modules inside the files they test,
as per the draft style guidelines.

Started a new module, path_util, for utility functions to do with
paths and directories.

Changed default_dest_dir to use a condition and return Path
instead of Option<Path>.
Add comments for the implementations of from_base64 and to_base64 for .
move rustdoc comments so that they attach to the functions rather than the impl blocks.
Doc review, as requested :-).

Mostly just phrasing things differently, which is a matter of taste. Feel free to use or not use any of the changes I'm suggesting.

I would say this one thing should be changed, though, not necessarily the way I changed it here.

     * Convert any string (literal, `@`, `&`, `~`)
     * that contains a base64 encoded value, to the byte values it encodes.

If this structure is going to be used, either the entire clause, 'that contains a base64 encoded value', should be bracketed by commas, or the comma at the end of the clause should be removed.
Merge pull request #1 from danluu/silly_style_changes

Doc review, as requested :-).
Add a lint mode for unused unsafe blocks/functions
core: remove unnecessary unsafe blocks/functions