Update README.
Use HTTPS clone URL in README.
Allow same-level layout blocks.
Change quantifier syntax.

Universal quantifiers now use the "for all" sign (∀), or the at sign (@)
as an ASCII approximation, rather than curly braces with commas. Stack
variables use a postfix horizontal ellipsis (…) or ASCII triple dot
(...) rather than a prefix dot. Vector accessors now use dot (.) instead
of at (@) in order to avoid confusion. Range operators now use dashes
instead of dots (– for .. and — for ...) or their ASCII approximations
(-- and --- respectively).
Allow polymorphic UDTs and matches with closures.

Type parameters are specified after the type name using the universal
quantifier symbol. Branches of 'match' expressions are now treated as
closures so that they correctly capture locals from enclosing scopes.
Allow matching on UDTs in interactive mode.
Silence spurious warning from GCC.
Lint.
Fix debugging information.
Make the result of relational operations Boolean.
Add basic streams library.

Streams have eagerly evaluated elements and lazily evaluated tails. They
are not memoized, and do not introduce reference cycles. Laziness is
encoded explicitly using nullary functions. Not all operations have been
ported from vectors to streams.
Update Emacs syntax highlighting.
Improve Emacs syntax highlighting.

Highlight character literals, built-in types, and primed identifiers.
Do not highlight keywords inside string literals.
Don't highlight identifier parts that look like intrinsics.
Improve mixfix syntax.

Makes underscores simpler to explain and disallows multi-word names.

Closes #123.
Adjust import.
Give unification an explicit expected/actual distinction.
Remove redundant 'leave 0' from inlined functions.
Eliminate redundant 'enter' instructions.
Improve IR assembly output.

Labels were not ending up in the flattened output, the 'comment'
constructor was unused, and activation data was not being shown
correctly or consistently.