Fixes after Brian's and Serg's comments: storage engine's unit tests
are now in storage/<engine>/unittest instead of unittest/storage/<engine>


BitKeeper/deleted/.del-Makefile.am~78ea2e42d44d121f:
  Delete: unittest/storage/maria/Makefile.am
BitKeeper/deleted/.del-Makefile.am~80497dbf1a80bdf3:
  Delete: unittest/storage/Makefile.am
storage/maria/unittest/ma_control_file-t.c:
  Rename: unittest/storage/maria/ma_control_file-t.c -> storage/maria/unittest/ma_control_file-t.c
config/ac-macros/plugins.m4:
  we change from unittest/storage/<engine>/ to storage/<engine>/unittest:
  if the engine is enabled has such a directory, build this directory,
  and add it to the list of unit tests to run.
configure.in:
  this dir does not exist anymore
storage/maria/Makefile.am:
  to build Maria unittests, libmaria must be built.
unittest/Makefile.am:
  unittest/storage is removed. target "unitests" is defined at
  "configure" time based on enabled engines.
storage/maria/unittest/Makefile.am:
  simple Makefile.am to build ma_control_file-t