Update create_transform.sgml

ref/create_transform.sgml调整内容191216

row3————————————————
	根据WinMerge比较结果，将
		"<refentry id="SQL-CREATETRANSFORM">"
		调整为小写
		"<refentry id="sql-createtransform">"

row290————————————————
	根据WinMerge比较结果，将
   		"CREATE LANGUAGE plpythonu ...;"
		调整为新内容
		"CREATE EXTENSION plpythonu;"
row318
	根据row290英文内容更新，将
   		"CREATE LANGUAGE plpythonu ...;"
		调整为新翻译内容
		"CREATE EXTENSION plpythonu;"

row309————————————————
	根据WinMerge比较结果，将
   		"   In practice, these commands would be wrapped up in extensions."
		调整为新内容
		"   In practice, these commands would be wrapped up in an extension."

Author: chegong18

postgresql/doc/src/sgml/ref/create_transform.sgml

@@ -1,6 +1,6 @@
 <!-- doc/src/sgml/ref/create_transform.sgml -->
 
-<refentry id="SQL-CREATETRANSFORM">
+<refentry id="sql-createtransform">
 <!--==========================orignal english content==========================
  <indexterm zone="sql-createtransform">
   <primary>CREATE TRANSFORM</primary>
@@ -287,7 +287,7 @@ ____________________________________________________________________________-->
 <programlisting>
 CREATE TYPE hstore ...;
 
-CREATE LANGUAGE plpythonu ...;
+CREATE EXTENSION plpythonu;
 </programlisting>
    Then create the necessary functions:
 <programlisting>
@@ -306,7 +306,7 @@ CREATE TRANSFORM FOR hstore LANGUAGE plpythonu (
     TO SQL WITH FUNCTION plpython_to_hstore(internal)
 );
 </programlisting>
-   In practice, these commands would be wrapped up in extensions.
+   In practice, these commands would be wrapped up in an extension.
   </para>
 ____________________________________________________________________________-->
   <para>
@@ -315,7 +315,7 @@ ____________________________________________________________________________-->
 <programlisting>
 CREATE TYPE hstore ...;
 
-CREATE LANGUAGE plpythonu ...;
+CREATE EXTENSION plpythonu;
 </programlisting>
    然后创建需要的函数：
 <programlisting>