Remove support for in-tree apr, apr-util and apr-memcache builds.  The
only external project we now build in-tree is SQLite.

* Makefile.in
  (SVN_EXTERNAL_PROJECT_SUBDIRS, external-all, external-install,
   external-clean, external-distclean, external-extraclean): Remove.
  (all, clean, distclean, extra-clean, install): Remove external support

* build/ac-macros/svn-macros.m4
  (SVN_EXTERNAL_PROJECT_SETUP, SVN_EXTERNAL_PROJECT): Remove.

* build/ac-macros/apr.m4: Don't look for source or setup as an external
   project, error on reconfig, tweak download message.

* build/ac-macros/aprutil.m4: Don't look for source or setup as an external
   project, error on reconfig, tweak name in messages, tweak download message.

* build/ac-macros/apr_memcache.m4: Don't look for source or setup as an
   external project.

* INSTALL: Remove in-tree details.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1456924 13f79535-47bb-0310-9956-ffa450edef68