Revision 59129

Backport from HEAD:

  Remove "location detection" from apu-config:

  * configure.in: Substitute APU_CONFIG_LOCATION as "build" or "source"
  appropriately.

  * apu-config.in: Set location to @APU_CONFIG_LOCATION@ rather than
  using fragile pwd/realpath guesswork.

  * Makefile.in (apu-config.out): New target.
  (install): Install apu-config.out instead of apu-config.

PR: 8867 (episode two)