Add a from_str function that calls out to the associated method on the trait
Add from_str docs
Fix glitches with struct field aligned indents
Indent correctly after opening square bracket
Allow indenting to align struct fields after curly brace
Indent return type to align with arguments
Add custom group for rust-mode
Add paragraph fill and auto-fill for multi-line comments
Add ERT tests
Add fractional second support to str{p,f}time

The ISO 8601 standard does not mandate any specific precision for
fractional seconds, so this accepts input of any length, ignoring the
part after the nanoseconds place. It may be more correct to round with
the tenths of nanoseconds digit, but then we'd have to deal with
carrying the round through the entire Tm struct (e.g. for a time like
Dec 31 11:59.999999999999).

%f is the format specifier that Python's datetime library uses for
0-padded microseconds so it seemed appropriate here.

cc #2350
move and duplicate macro defns in sha2 to make them hygienic

... it would also have been possible to add all of their dependencies,
but that would have increased the already-lengthy list of parameters.
Also, if we had macros that could expand into macro defns, you could
stage it. This seemed like the least painful choice.
disallow ident equality checks when contexts are not equal
fix for issue #7588, overflow now handled correctly
commenting out special Eq implementation for now

See the comments for details on why I'm leaving this code
in, though commented out.
rename resolve to mtwt_resolve
ident->name
compare macro tokens hygienically (commented out)
try removing basically dead code in resolve
add hygiene support fns, move them around.

also adds test cases
one-line comment