configure: add fallback when checking for ar
TR: Prevent internal error on `begin-for-syntax`

Closes PR 13878

Please merge to v6.0
Caveat section on macros/phase-1+ code in TR

Please merge to v6.0
Improve type of `negate`

Now for functions with simple filters, it'll negate the
filters so that, e.g., (negate string?) can be used with
occurrence typing.

Please merge to v6.0
fix/expand/improve docs on "config.rktd"

Merge to v6.0
make installers: install required packages, first

This change should fix a problem with the Mac OS X PPC build,
where the "libsqlite3" shared library needs to be installed
early. The same strategy is already used for Windows.

Merge to v6.0
define-runtime-path: add support for version search to 'so form

Merge to v6.0
fix focus

please include in the 6.0 release
racket/gui cocoa: fix crashing bug with `combo-field%`

Merge to v6.0
racket/gui cocoa: fix border of `combo-field%` for recent Mac OS X

Merge to v6.0
Ensure that threads created within call-with-limits are accounted during the time/space limits
fix line breaking for text/font

please include on the 6.0 release branch
enable `raco exe` tests for DrDr

I meant to try this back in 0bc89dc6.
fix `raco config --set`

Merge to v6.0
fix README instructions on `raco pkg config --set name`

Merge to v6.0
reflow release notes for v6.0

Merge to v6.0
improve hash/c contracts

closes PR 14189

please include on the release branch
fix grammar and spelling

please include in the release branch
the color-blindness color schemes are not yet ready for release

Please merge to the release branch
restore the color schemes

please do NOT merge to the release branch