Bug#18564 Test failure due to test not checking preconditions

 - Add variable "have_dynamic_loading" and use it to check if the udf test should be run.


mysql-test/include/have_udf.inc:
  Use variable "have_dynamic_loading" to to determine if there is support for udf's
mysql-test/r/have_udf.require:
  Use variable "have_dynamic_loading" to to determine if there is support for udf's
mysql-test/t/disabled.def:
  Remove udf from disabled
sql/mysql_priv.h:
  Add have_dlopen variable
sql/mysqld.cc:
  Add have_dlopen variable
sql/set_var.cc:
  Add have_dlopen variable and name it "have_dynamic_loading" in "SHOW VARIABLES"

mysql-test/include/have_udf.inc

 #
-# To check if the udf_example.so is available,
-# try to load one function from it.
-#
+# Check if server has support for loading udf's
+# i.e it will support dlopen
 #
 --require r/have_udf.require
---disable_abort_on_error
-CREATE FUNCTION metaphon RETURNS STRING SONAME 'udf_example.so';
---disable_query_log
-DROP FUNCTION metaphon;
---enable_query_log
---enable_abort_on_error
+disable_query_log;
+show variables like "have_dynamic_loading";
+enable_query_log;

mysql-test/r/have_udf.require

-CREATE FUNCTION metaphon RETURNS STRING SONAME 'udf_example.so';
+Variable_name	Value
+have_dynamic_loading	YES

mysql-test/t/disabled.def

@@ -12,4 +12,3 @@
 
 sp-goto         : GOTO is currently is disabled - will be fixed in the future
 ndb_load        : Bug#17233
-udf             : Bug#18564 (Permission by Brian)

sql/mysql_priv.h

@@ -1296,7 +1296,7 @@ extern SHOW_COMP_OPTION have_ndbcluster;
 #endif
 
 extern SHOW_COMP_OPTION have_isam;
-extern SHOW_COMP_OPTION have_raid, have_openssl, have_symlink;
+extern SHOW_COMP_OPTION have_raid, have_openssl, have_symlink, have_dlopen;
 extern SHOW_COMP_OPTION have_query_cache;
 extern SHOW_COMP_OPTION have_geometry, have_rtree_keys;
 extern SHOW_COMP_OPTION have_crypt;

sql/mysqld.cc

@@ -474,7 +474,7 @@ CHARSET_INFO *character_set_filesystem;
 
 SHOW_COMP_OPTION have_isam;
 SHOW_COMP_OPTION have_raid, have_openssl, have_symlink, have_query_cache;
-SHOW_COMP_OPTION have_geometry, have_rtree_keys;
+SHOW_COMP_OPTION have_geometry, have_rtree_keys, have_dlopen;
 SHOW_COMP_OPTION have_crypt, have_compress;
 
 /* Thread specific variables */
@@ -6415,6 +6415,11 @@ static void mysql_init_variables(void)
 #else
   have_symlink=SHOW_OPTION_YES;
 #endif
+#ifdef HAVE_DLOPEN
+  have_dlopen=SHOW_OPTION_YES;
+#else
+  have_dlopen=SHOW_OPTION_NO;
+#endif
 #ifdef HAVE_QUERY_CACHE
   have_query_cache=SHOW_OPTION_YES;
 #else

sql/set_var.cc

@@ -810,6 +810,7 @@ struct show_var_st init_vars[]= {
   {"have_compress",	      (char*) &have_compress,		    SHOW_HAVE},
   {"have_crypt",	      (char*) &have_crypt,		    SHOW_HAVE},
   {"have_csv",	              (char*) &have_csv_db,	            SHOW_HAVE},
+  {"have_dynamic_loading",    (char*) &have_dlopen,	            SHOW_HAVE},
   {"have_example_engine",     (char*) &have_example_db,	            SHOW_HAVE},
   {"have_federated_engine",   (char*) &have_federated_db,           SHOW_HAVE},
   {"have_geometry",           (char*) &have_geometry,               SHOW_HAVE},