ghc needs it to fail to correctly detect it for later.

(cherry picked from commit 70b8ab6)

(cherry picked from commit fdc6caf)

This removes the 1.29 backport and replaces it with the 1.31 version
from master.

jemalloc with stripped prefix would cause segfaults in free:
NixOS/nixpkgs#49557 (comment)

This commit has been adjusted from the one on master to only carry the
relevant changes (the new optional `stripPrefix`) flag while still
keeping the other flags that were removed on master since they are no
loner supported by the version used there.

(cherry picked from commit 973eca7)

Firefox >=65 will depend on icu >=63. All the older firefox versions
(and derived packages) seem to work fine with this change.

Also the system path environment patch will fail to apply since there
was a trivial whitespace change in the source file. By adding `-l` to
patch we can avoid having to track two patches that do basically the
same. Having patchFlags per file without resorting to pre-/postPatch
would be nicer but there doesn't seem to be a facility for that right
now.

(cherry picked from commit e37b765e7897c015153552d4e33a8571ab9c5457)

v6.1-20181027 url is 404.

(cherry picked from commit 138720f)

Development releases of ncurses are uploaded but often also removed
again. This is causing a lot of trouble, so let's instead use a
GitHub mirror.

(cherry picked from commit 43e867a)

[18.09] firefox 65

There have been some more changes to the source tree which broke the
buildconfig patch. This commit adds another patch that can be used for
the future versions. Once all the flavors are based off a new(ish)
firefox release we can remove the old patch.

(cherry picked from commit 10024f2)

[18.09] nss 3.41 -> 3.42, firefox 64 -> 65

(cherry picked from commit 4fbce62)