Copy stable/11@r303970 to releng/11.0 as part of the 11.0-RELEASE
cycle.

Prune svn:mergeinfo from the new branch, and rename it to RC1.

Update __FreeBSD_version.

Use the quarterly branch for the default FreeBSD.conf pkg(8) repo and
the dvd1.iso packages population.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC libunwind improvements

r302450: libunwind: update to upstream snapshot r272680

The key improvement is that it may be built without cross-unwinding
support, which significantly reduces the stack space requirement.

r302456: libunwind: enable only the native unwinder by default

This significantly reduces stack space requirements, and runtimes
require only native unwinding.

r302475: libunwind: limit stack usage in unwind cursor

This may be reworked upstream but in the interim should address the
stack usage issue reported in the PR.

r303016: llvm-libunwind: use conventional (non-Darwin) X86 register numbers

For historical reasons Darwin/i386 has ebp and esp swapped in the
eh_frame register numbering. That is:

Darwin Other
Reg # eh_frame eh_frame DWARF
===== ======== ======== =====
4 ebp esp esp
5 esp ebp ebp

Although the UNW_X86_* constants are not supposed to be coupled to
DWARF / eh_frame numbering they are currently conflated in LLVM
libunwind, and thus we require the non-Darwin numbering.

PR: 206384
Approved by: re (kib)
Sponsored by: The FreeBSD Foundation

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Bring LLVM libunwind snapshot into contrib/llvm/projects

Import LLVM libunwind snapshot revision 246528

From https://llvm.org/svn/llvm-project/libunwind/trunk/