Bug#932367: GAP_Initialize signature changed

[Martin von Gagern]

I tried locally rebuilding sagemath against GAP 4r10p2-2. It seems we
need https://github.com/sagemath/sage/commit/e6e80bfa0f36688904716f93e04ad0121b7a4136.patch
to account for changes to the GAP_Initialize signature from
https://github.com/gap-system/gap/commit/5dad0ef01e5527d83d7ade6677891b855381aee3
and https://github.com/gap-system/gap/commit/eab71117db3a3afd1adec9a87e96b3b4a9414f60.

Unfortunately the patch doesn't apply cleanly, and I don't have time
just now to massage it. So I'm sending what information I have in case
someone else can cherry-pick it in.

Without this, I get a SIGSEGV when loading sage.libs.gap.libgap
because the address of a data structure (the old env argument) is
treated as a function pointer that gets called during garbage
collection. The error doesn't stop the build at that point, but it
causes the documentation build to hang indefinitely eventually,
similar to bug #901532. Check sage/logs/dochtml.log for the actual
problem report.