scribble: fix PDF rendering for image without bounding-box info

Merge to v6.1
(cherry picked from commit 09b4445c7a28b1d8fc3feb2d4ab7a64e9a991a8a)
scribble: another Unicode mapping for Latex output

This mapping is needed by the "redex-unstable" documentation.

Merge to v6.1
(cherry picked from commit a33c64b45f54404c50741f04137c62fbe5c4efe2)
update racket/HISTORY.txt

Merge to v6.1
(cherry picked from commit e8278176fa82484d708f5bb783a493dc29551af7)
update HISTORY.txt for 6.1

Please include in the 6.1 release
(cherry picked from commit fbc3d7ea7c8506724c86efccbd40b9b8f24fcacf)
update HISTORY for 6.1

Please include in the 6.1 release
(cherry picked from commit 5168764293e0bb76d6c07e502c7305837f947af1)
fix stxparse test
(cherry picked from commit 4f05e33192efc9cc818084c4e9d5d65ec3570d0d)
fixed macro stepper test
(cherry picked from commit f4978d2fdbcb9365f6e3c13455547cf825bf9f15)
Reorder some recursive definitions to avoid undefined references.

Please include in v6.1 release if possible.
(cherry picked from commit 45306397ccaadfd72a39a88c25a0e4acf37f04f4)
fix compatible-closure to deal properly with language extension

Thanks to David Van Horn for spotting the problem and providing
a nice simple test case

Please include in 6.1
(cherry picked from commit 3666842cd452ba80e139838c23038fc231c49ddb)
updated HISTORY.txt

Merge to 6.1 release
(cherry picked from commit c970a0656cf7d75a5eac356c6a72c7dfbc33c38d)
Update TR history.

Please merge to 6.1.
(cherry picked from commit 5a12f8e778a017c836be4d3b7122d8256e25ddb6)
remove call to 'time'

Please add to 6.1 release branch
(cherry picked from commit cdd06f108ca7ecb2ce4a1a471566b0863a2a4fad)
racket/draw: fix `get-argb-pixels` for unscaled and just-alpha

Closes PR 14653

Merge to v6.1
(cherry picked from commit 295cb46c48bd70c1158bdc5e2b1f285b4ac2d086)
Fix `compiled-bitmap` and `compiled-bitmap-list` on 2x bitmaps, lossy compression

This fixes the docs for `compiled-bitmap-list`. Icons in DrRacket were immune,
because they're stored in modules as PNG bytes.

Please merge to v6.1
(cherry picked from commit 1f7b452920dd6421e25fd02fa2cf9036acc9a2ce)
Move `margin-note*` in math docs to work around issue with Firefox

Please merge to v6.1
(cherry picked from commit 3849643e4b9826cbf8091bfbded56506f0f62bc9)
documented addition of check-random; please include in 6.1
(cherry picked from commit 68de6454d91129041b0284c7ce7c3b4ca596b494)