file/untgz: fix race
Minor improvements to version-specific download pages.
Improve srfi-std html files.

Re-encode in UTF-8, and for the main page also improve the text with
some racket-isms.  (Could use much more work, of course.)
Generalize type of curry to functions of arity 3+.
Fix TR contracts.
Fix the fix to TR contracts.
support for keyword argumnets + transfer-option, exercise-option and waive-option do not raise an error on values without an option
Add template file for tweaked docs.
Change the symlink that serves docs to the one that holds the tweaked version.
fix unstable/2d's lexer to handle eof better
add with-roots to plai's gc languages
fix lexer contract
adjust scribble-lexer test to handle errors
Modify the src-pos error reporting in parser-tools to better show the token context.

Addresses PR 9924.
add experimental support for "phaseless" modules

The intent is to support phase-crossing data such as the `exn:fail:syntax'
structure type that is instantiaed by macros and recognized by contexts
that use `eval' or `expand'. Phaseless modules are highly constrained,
however, to avoid new cross-phase channels, and a module is inferred to
be phaseless when it fits syntactic constraints.

I've adjusted `racket/kernel' and improved its documentation a little
so that it can be used to implement a phaseless module (which can
import only from other phaseless modules).

This change also adds a `flags' field to the `mod' structure type
from `compiler/zo-structs'.
Enable contract and add a purpose statement
Various improvements to Guide section 3

  * Examples
  * Scheme -> Racket
  * Grammar & style
fix some "phaseless" module holes
try "phase-collapsing" instead of "phaseless"
add `racket/kernel/init'