generalize rule-pict-style to allow more customization of reduction-relation layouts
unix-installer test: check "natipkg"
Scribble HTML: included needed tag prefixes in "Link to this section"
Fix checking of (list ...) w/ union expected type

Closes PR 14758
Closes PR 14747
Avoid computing type tooltips twice

The logging code in tc-toplevel.rkt is sufficient to get
all the type tooltips.
Mac OS X .pkg installer: check for target folder before installing

If the target folder exists, let the user know and give up. (This
seems safer than trying to delete the folder, since there might be
other files in the folder than the original files, and the installer
doesn't currently keep a list of installed files.)
distro-build: try connecting a few times to let a VM warm up

This strategy has been successful for the package-build service,
and it will hopefully cut down on spurious snapshot build failures
that happen when a VM's networking doesn't start up quickly enough.
Fix set-symmetric-difference docs.
Fix bug with equal? on small bit-vectors.
Fix init order of choice%'s type
Synch German string constants with latest.
meta/pkg-build: fix potential problem with cycle detection

Also, correct typos and out-of-date information in comments that
serve as documentation.
meta/pkg-build: add support for "minimal" vs. full VMs

Try building on a minimal VM, first, and then fall back to a more
general VM is that fails. For example, a minimal VM might not include
a C compiler, which can help clarify that a package will work in some
environments and not in others.
meta/pkg-build: run `raco test --drdr` for each package
meta/pkg-build: always set the VM clock

Consistent installation depends on a global clock that always
moves forward, so make sure VMs stay in sync.
meta/pkg-build: keep test-success log (same as test-failure)
simplify and extend the find-string method in text%

This implementation runs about 10% faster than the old when searching
for "λ" in (collection-file-path "unit.rkt" "drracket" "private"). It
is copied directly from the search search algorithm from Wikipedia
called Knuth-Morris-Pratt, but with a fancier version of get-char that
cooperates with text%'s snip interface for more efficient linear
scans of characters.

It also generalizes the previous one by supporting searching into
embedded text% objects inside editor-snip% objects

related to PR 14688
related to PR 14687
fix incorrect contact; closes PR 14798

please include in the 6.1.1 release
Use the scale when rendering svg

Thanks to Antonio Menezes Leitao for the change
meta/pkg-build: add an "about" page

Explain `raco test`, the `PLT_PKG_BUILD_SERVICE` environment variable,
and the "x86_64-linux-natipkg" platform.