Remove useless use of undocumented submodules.
Remove useless use of optionSet.
Add error an message to prevent use of useless submodules.
mariadb: Patch to compile on OS X.

* perl is required at build time on darwin. Copied from the
  mysql/5.5.x.nix

* CMake on darwin creates shared libraries with relative 'install_name'
  paths which are made absolute by fixDarwinDylibNames.

  See http://answers.opencv.org/question/4134/cmake-install_name_tool-absolute-path-for-library/

* The asm patch was needed to compile on darwin, though I do not
  understand what is going on. Error before the patch:

  [ 15%] Building C object mysys/CMakeFiles/mysys.dir/my_context.c.o
  .../nix-build-mariadb-10.0.13.drv-1/mariadb-10.0.13/mysys/my_context.c:207:Unknown pseudo-op: .cfi_escape
  .../nix-build-mariadb-10.0.13.drv-1/mariadb-10.0.13/mysys/my_context.c:207:Rest of line ignored. 1st junk character valued 48 (0).
  make[2]: *** [mysys/CMakeFiles/mysys.dir/my_context.c.o] Error 1