Fix a bug in codegen for non-updatable selector thunks (#8817)

To evaluate most non-updatable thunks, we can jump directly to the
entry code if we know what it is.  But not for a selector thunk: these
might be updated by the garbage collector, so we have to enter the
closure with an indirect jump through its info pointer.

(cherry picked from commit b1ddec1e6d4695d71d38b59db26829d71ad784e1)
fix comment on allocate() (#8254)

(cherry picked from commit 68c0d8689dd93cb0ce74a288e82f2ed997c31acc)
Add hs_thread_done() (#8124)

See documentation for details.

(cherry picked from commit af6746fb6b5adb5ba5be6e0f647c4ebe767ce084)
PPC: Fix loads of PIC data with > 16 bit offsets (#7830).

Loads should now handle up to 32 bit offsets.

(cherry picked from commit 67029f200c5512f8ba5b9b7c25a5d1131422ef8e)
Documentation updates for 7.8.1 release

Notably, GND is now usable with Safe Haskell. Also, Coercible now is in
Data.Coerce canonically, and we added some more instances.

Signed-off-by: Austin Seipp <austin@well-typed.com>
(cherry picked from commit 71611523c25bb89b81e789d5a2dd3d5d9754b025)
Fix binary-dist target with xz/gzip

This was harmless but annoying: we forgot to take the compression
extention into account when copying the binary dist out of bindistprep

Signed-off-by: Austin Seipp <austin@well-typed.com>
(cherry picked from commit 025a66e7fc416ab9ee1df56ad26dfe6232d32900)
Note that we need Cabal-1.18 in the release notes

Thanks to George Colpitts for helping us remember this!

Signed-off-by: Austin Seipp <austin@well-typed.com>

(cherry picked from commit f9627252fc278ecaafbb1885c31adad7357c0763)
binary-dist: when using xz, use extreme compression.

When building a binary distribution with TAR_COMP=xz, using the -9e flag
(extremely high compression) results in substantial savings: for the
Mavericks builds, bzip2 scores in at about 120mb, while xz at level 9
scores about 60mb - a huge reduction!

This of course takes significantly longer - but it does not affect
decompression speed for end users, so it's certainly worth it.

Signed-off-by: Austin Seipp <austin@well-typed.com>

(cherry picked from commit 251b18aba97329ff41b8479ff78d38505cf086f8)