Fix "make check" to be able to find ab, creating a "bin" inside the

dummy install root at $builddir/check.

* Makefile.in (check-binaries): New target.
  (check/bin/apxs): Moved target inside check/bin.
  (check/build/config_vars.mk): Override bindir as well.
  (check): Use apxs at new location.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1832011 13f79535-47bb-0310-9956-ffa450edef68