serfmake: add install target; support --with-apr param to find APR & APR-util; support --prefix for installation targeting.
serfmake: add install target; support --with-apr param to find APR & APR-util;
support --prefix for installation targeting.

* serfmake
  (shutil): Import.
  (main): Build up a parameter map of command line args; pass params to cmds.
  (cmd_build, cmd_check): Give Builder the parameter list.
  (cmd_install): Implement.
  (cmd_clean): Take param arg.
  (Builder.__init__): Call APR/APUConfig with the apr params; set libdir,
  includedir, and install mode.
  (Builder.load_deps): Store our built header list in ourselves.
  (Builder.install_target): Copy headers and libraries to our destination.
  (ConfigScript.__init__): Append extra search dirs to our list.

jandre/serf,jandre/serf,jandre/serf,jandre/serf