eclass: update prefix eclass

The prefix eclass is out of date. In particular, it doesn't include the
hprefixify function, which is used by:
   * app-text/texi2html
   * dev-lang/ghc
   * dev-python/matplotlib

This change updates the eclass from upstream.

BUG=chromium:885210
TEST=`emerge-soraka matplotlib` no longer has 'hprefixify: command not
     found' in its build message.

Change-Id: I8ae30b72922602beda15ec2c40d3be9db92fd73f
Reviewed-on: https://chromium-review.googlesource.com/1231114
Commit-Ready: Alex Khouderchah <akhouderchah@chromium.org>
Tested-by: Alex Khouderchah <akhouderchah@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
1 file changed