made the install-plt menu item's browse
file dialog show files with ".plt" by default.

Also, clarified the docs for finder:default-extension

closes PR 13104
Added von Mangoldt function
Renamed polygonal functions to include -number the name.
fix untagged cpointer as place-channel message

(repair by Kevin)

Closes PR 13282
JIT: fix allocation of came-lambda closures over flonums

Also, clean up code and assumptions related to fixnum-producing
functions and unboxing (not related to the bug).
fix quoted submodule path in `all-from-out'
avoid calling client->screen with numbers out of its domain

related to PR 13292
raco setup: build database mapping doc tags to "out.sxref"s

The `xref' produced by `setup/xref' uses the database to delay
loading "out.sxref"s, which cuts 64-bit DrRacket's initial
footprint by around 50MB (i.e., about 20%).
db: add `sqlite3-available?'

Loading `db/sqlite3' no longer raises an exception if
the SQLite library isn't found. Instead, `sqlite3-connect'
raises an exception, while `sqlite3-available?' reports
whether it will work.

The dynamic test allows the documentation-help system
to continue to work if SQLite3 is not available. Currently,
though, `raco setup' still insists on using SQLite3 to
build the database of documented tags.
racket/serialize: simpler handling of quotable values
fixup for docindex.sqlite
net/imap: log to an 'imap logger
serialize bluebox tables

Typically, the bluebox table includes keys that have interned parts,
so serialization can save space both on disk and in memory when the
bluebox information is reloaded.
break cross-reference info for document into pieces

For example, the cross-reference information for the
Reference is now broken into about 16 pieces, so that
resolving a cross-reference into the Reference doesn't
require loading all cross-reference information for
the Reference.

Every document is split into two pieces, so that the title
of a document is roughly in its own piece. That way,
re-building the page of all installed documentation can be more
scalable (after some further changes).
raco setup: move doc dependency and duplicate checking to database

This change makes document building --- and specially incremental
document building --- more scalable. The global duplicate-definition
check is handled by a database query, for example.
dist-spec fix

probably temporary, until the tree library moves
New Racket version 5.3.1.9.
don't fail when there's no user-specific docindex
Added more margin notes
Synch German string constants with latest.