Import elftoolchain rev 3130

From svn.code.sf.net/p/elftoolchain/code/trunk
Copy elftoolchain top-level directory from vendor at r260684

Subdirectories are copied from r276062.

This will allow 'svn merge' at the elftoolchain top level to work
properly. Previously only the subdirectories were related to the vendor
branch according to svn metadata, which meant they would have to be
merged individually.
Update elftoolchain to upstream rev 3130

This brings a number of fixes to elfcopy/strip and DWARF4 improvements.

Sponsored by:	The FreeBSD Foundation
Attach vtnet to virtio_mmio. Qemu provides this as an option with AArch64.

Sponsored by:	The FreeBSD Foundation
Update elftoolchain to upstream rev 3130

This includes a number of libdwarf improvements (particularly DWARF4
related) and updates to elftoolchain tools such as strip(1). It also
includes a large number of miscellaneous fixes (memory leaks, sign and
cast warnings, integer overflow and underflow, etc.).

This is a merge of r276167,276170-276172 from the
projects/elftoolchain-update-r3130 branch.

Sponsored by:	The FreeBSD Foundation
Restore r276252 mdoc fix

It was accidentally reverted in the elftoolchain update (r276371).

Sponsored by:	The FreeBSD Foundation
Rename DT_FEATURE_1 to DT_FEATURE

Track r270303:

  This provides a minor cleanup in elfdump; there are otherwise no
  consumers in the tree.  Old SUN documentation can be found for either
  variant, but GNU binutils switched to DT_FEATURE around 2000.

Sponsored by:	The FreeBSD Foundation
libelf: Do not read past end of buffer

Previously a corrupt ELF file could read beyond the end of e_rawfile.

Upstream elftoolchain ticket 462.  Found via the security/afl fuzzer.

Sponsored by:	The FreeBSD Foundation
- No longer exclude malo(4) and mwl(4), they have been fixed in r275870
  and r275871 respectively to build with PAE enabled.
- For the PAE kernel configuration file, no longer exclude devices that
  are known to be 64-bit DMA clean from amd64.

MFC after:	3 days
mdoc: sort SEE ALSO.
mdoc: sort SEE ALSO.
Delay dropping to the mountroot prompt for 10 seconds
in case the root device is not yet ready.

Sponsored by:	The FreeBSD Foundation