Restore r276252 mdoc fix

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

Sponsored by:	The FreeBSD Foundation


git-svn-id: svn+ssh://svn.freebsd.org/base/head@276372 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
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


git-svn-id: svn+ssh://svn.freebsd.org/base/head@276373 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f