net/http-client: fix `http-conn-live?` result

Merge to v6.0
(cherry picked from commit 1f6453de8959adc6a9b1fc3e7ef78fbf202e10b9)
Synch German string constants with latest.
(cherry picked from commit 019c8214ef42ca917cd4a075c1d980453e347f82)
fix a synchronization problem in the GC for places

When a GC is needed for the shared space, a GC is triggered
in all places, and the places wait until each other place
has completed. However, the places also need to wait until
all other places are ready to *start* a GC; otherwise, a
place may be modifying a shared record while some other place
traverses it for a GC.

Closes PR 14229

Merge to v6.0
(cherry picked from commit 280bb31d70f50a4a3d4e36ba9d069098383c2dfb)
Add more documentation for `Procedure` type

Please merge to v6.0
(cherry picked from commit 1243d12248214d8e261a0496f273fe1ea7127e28)
Describe how to make packages compatible with 5.3.5 and 5.3.6.

As requested by Sam Tobin-Hochstadt on the mailing list today.

Merge to v6.0
(cherry picked from commit c80f92885d0b5508c51029424eec2c42409eb60c)
Remove extraneous compile of non existent file.

Merge to v6.0
(cherry picked from commit 83ce25294cc158e9fddc00a1c7f229fa10a5d580)
Add tests for some recent base type additions
(cherry picked from commit 78820bda4528ca100524d5007cf46905d039803d)
Fix types for `remove` and friends.

A few of these had unnecessary uses of type variables.
The type for `remove*` was unsound.

Please merge to v6.0
(cherry picked from commit a98e4c5474f83cc146b62baf64c3fa2ee8132fef)
Mac OS X: fix executable creation for LC_DYLIB_CODE_SIGN_DRS

The LC_DYLIB_CODE_SIGN_DRS load command is relatively new, and
it needs to be updated when we shift __LINKEDIT to add
__PLTSCHEME.

Merge to v6.0
(cherry picked from commit 861384d36d35b046ed666d238046a57ff589ed9c)
Add types to hasheq and hasheqv.

Merge to 6.0.
(cherry picked from commit 48a16b2b8a6cb0af6607a3056f6723f34da855f3)
fix reducing arity or chaperoning keyword-valued `prop:procedure`

Fix various problems, including a bad result from `procedure-arity`
and problems with chaperones and arity error messages when a
structure's `prop:procedure` value is a keyword-accepting procedure.

Merge to v6.0
(cherry picked from commit 0b48e883da14a3ccfd92ba5aad408f1706fdaead)
Better error msg for annotations on unbound ids

Closes PR 14246

Please merge to v6.0
(cherry picked from commit f1d35f6ec94e1c9dff2d149c5f7f7a777a78f547)
Quote the identifier in the declaration error msg

Please merge to v6.0
(cherry picked from commit 34c5b327463db014fb0d3c42922d60e75e4ada63)
fix `for-label` import of a submodule

Closes PR 14155

Merge to v6.0
(cherry picked from commit 80d0b2fcc330b44b1ca614c173a35cb8058b656f)
fix incorrect propagation of name via `syntax-local-name`

Merge to v6.0
(cherry picked from commit 4abe7d2657ca9f39284a5f1c0ef5adc626731376)