- Update for 5.1
 - Add "have_dlopen"
 - Remove requirement to load udf's only in "opt_plugin_dir" 


include/my_global.h:
  Remove duplicate defines
mysql-test/include/have_udf.inc:
  Use "have_dlopen" to check if we "have udf"
mysql-test/r/have_udf.require:
  Use "have_dlopen" to check if we "have udf"
mysql-test/r/udf.result:
  Update for new error message "function"->"symbol"
sql/item_func.cc:
  Remove "evil" dbug printour that checks args[0] even if arg_count is 0
sql/mysql_priv.h:
  Add "have_dlopen"
sql/mysqld.cc:
  Add "have_dlopen"
  Move HAVE_DLOPEN defined to only surround "udf_free" and "udf_init"
sql/set_var.cc:
  Add "have_dlopen"
sql/sql_plugin.cc:
  Surround 'dlclose' with HAVE_DLOPEN
sql/sql_udf.cc:
  Remove the requirement to load udf's only from "opt_plugin_dir".
  Fix spelling error