Make filters on mutated/undefined vars an error.

Closes PR 14422.
Closes PR 14495.
Make error messages better for function types with bad filters.

Also makes it so filters are not parsed as keyword types.

Closes PR 14492.
Closes PR 14520.
Add code to handle when the test expression is neither true nor false.

Closes PR 14564.
Remove debug lines and commented cases

This helps for editing in paredit
Check function depth for parsing object indices

Closes PR 14509
meta/pkg-build: check dependency declarations

Uses `raco setup --check=pkg-deps --pkgs <pkg>`.
meta/pkg-build: first cut at result-summary page

Summary also goes in "summary.rktd", so a different view
can be generated.
refine attempt at debugging output for JIT buffer overflow
pkg-build/thread: fix test
read: fix long-double error reporting

This repair corrects an ocassional test failure in the `read`
test suite.
fix doc typo
games/gobblet: fix game explorer in case of tie

A tie due to a cycle would cause the explorer to fail instead of
giving up with a tie.
meta/pkg-build: extract/salvage docs for conflicting and failed packages

Also, add a step to package results into a web-friendly archive.
meta/pkg-build: fix construction of catalog URL

Also, add a `#:skip-download?` option.
meta/pkg-build: better way to select build steps
Include pkg authors in status web page.
pkg-build: tweak format of summary page
meta/pkg-build: use Etag header to avoid installer download
Post-release version for the v6.1 release
add #:post condition to meta functions