Bug#17112 - SHOW PLUGIN should be SHOW PLUGINS

sql/lex.h:
  SHOW PLUGINS - BUG#17112
sql/sql_yacc.yy:
  SHOW PLUGINS - BUG#17112

sql/lex.h

@@ -396,6 +396,7 @@ static SYMBOL symbols[] = {
   { "PASSWORD",		SYM(PASSWORD)},
   { "PHASE",            SYM(PHASE_SYM)},
   { "PLUGIN",           SYM(PLUGIN_SYM)},
+  { "PLUGINS",          SYM(PLUGINS_SYM)},
   { "POINT",		SYM(POINT_SYM)},
   { "POLYGON",		SYM(POLYGON)},
   { "PRECISION",	SYM(PRECISION)},

sql/sql_yacc.yy

@@ -501,6 +501,7 @@ bool my_yyoverflow(short **a, YYSTYPE **b, ulong *yystacksize);
 %token  PARAM_MARKER
 %token  PHASE_SYM
 %token  PLUGIN_SYM
+%token  PLUGINS_SYM
 %token  POINTFROMTEXT
 %token  POINT_SYM
 %token  POLYFROMTEXT
@@ -8170,6 +8171,15 @@ show_param:
               YYABORT;
 	  }
         | PLUGIN_SYM
+	  {
+	    LEX *lex= Lex;
+	    WARN_DEPRECATED(yythd, "5.2", "SHOW PLUGIN", "'SHOW PLUGINS'");
+            lex->sql_command= SQLCOM_SELECT;
+            lex->orig_sql_command= SQLCOM_SHOW_PLUGINS;
+            if (prepare_schema_table(YYTHD, lex, 0, SCH_PLUGINS))
+              YYABORT;
+	  }
+        | PLUGINS_SYM
 	  {
 	    LEX *lex= Lex;
             lex->sql_command= SQLCOM_SELECT;
@@ -9358,7 +9368,6 @@ keyword:
 	| OPEN_SYM		{}
         | PARSER_SYM            {}
 	| PARTITION_SYM		{}
-        | PLUGIN_SYM            {}
         | PREPARE_SYM           {}
 	| REMOVE_SYM		{}
 	| REPAIR		{}
@@ -9539,6 +9548,8 @@ keyword_sp:
 	| PARTITIONS_SYM	{}
 	| PASSWORD		{}
         | PHASE_SYM             {}
+        | PLUGIN_SYM            {}
+        | PLUGINS_SYM           {}
 	| POINT_SYM		{}
 	| POLYGON		{}
         | PRESERVE_SYM          {}
@@ -9552,7 +9563,7 @@ keyword_sp:
         | REBUILD_SYM           {}
         | RECOVER_SYM           {}
 	| REDO_BUFFER_SIZE_SYM	{}
-	| REDOFILE_SYM  	{}
+	| REDOFILE_SYM          {}
         | REDUNDANT_SYM         {}
 	| RELAY_LOG_FILE_SYM	{}
 	| RELAY_LOG_POS_SYM	{}