Update elftoolchain to upstream rev 3130

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