Plugins included into bin release cannot be
    installed on debug version of server

Ensure that the plugin files of the debug build
get into the optimized tree, so that they find
their way into the final RPMs.


support-files/mysql.spec.sh:
  Use "make install" in the debug build tree to get the debug
  plugin files to a temporary location,
  then move them to "plugin/debug/" in the optimized build tree
  so that the install hook in "plugin/Makefile.am" forwards them
  into the final installation.
  
  This fixes bug#49022 for the generic RPMs.
  
  Unrelated:
  The plugin objects were listed twice in the file list,
  do a cleanup.