docs: document which server-side languages can create procs

This was missed when the feature was added.

Reported-by: Daniel Westermann

Discussion: https://postgr.es/m/160624532969.25818.4767632047905006142@wrigleys.postgresql.org

Backpatch-through: 11

Author: bmomjian

doc/src/sgml/plperl.sgml

@@ -13,13 +13,13 @@
 
   <para>
    PL/Perl is a loadable procedural language that enables you to write
-   <productname>PostgreSQL</productname> functions in the
+   <productname>PostgreSQL</productname> functions and procedures in the
    <ulink url="https://www.perl.org">Perl programming language</ulink>.
   </para>
 
   <para>
    The main advantage to using PL/Perl is that this allows use,
-   within stored functions, of the manyfold <quote>string
+   within stored functions and procedures, of the manyfold <quote>string
    munging</quote> operators and functions available for Perl.  Parsing
    complex strings might be easier using Perl than it is with the
    string functions and control structures provided in PL/pgSQL.

doc/src/sgml/plpgsql.sgml

@@ -19,7 +19,7 @@
     <itemizedlist>
      <listitem>
       <para>
-       can be used to create functions and triggers,
+       can be used to create functions, procedures, and triggers,
       </para>
      </listitem>
      <listitem>
@@ -34,7 +34,7 @@
      </listitem>
      <listitem>
       <para>
-       inherits all user-defined types, functions, and operators,
+       inherits all user-defined types, functions, procedures, and operators,
       </para>
      </listitem>
      <listitem>

doc/src/sgml/plpython.sgml

@@ -8,7 +8,7 @@
 
  <para>
   The <application>PL/Python</application> procedural language allows
-  <productname>PostgreSQL</productname> functions to be written in the
+  <productname>PostgreSQL</productname> functions and procedures to be written in the
   <ulink url="https://www.python.org">Python language</ulink>.
  </para>
 

doc/src/sgml/pltcl.sgml

@@ -16,7 +16,7 @@
    <productname>PostgreSQL</productname> database system
    that enables the <ulink url="https://www.tcl.tk/">
    Tcl language</ulink> to be used to write
-   <productname>PostgreSQL</productname> functions.
+   <productname>PostgreSQL</productname> functions and procedures.
   </para>
 
   <!-- **** PL/Tcl overview **** -->

doc/src/sgml/spi.sgml

@@ -11,7 +11,7 @@
   The <firstterm>Server Programming Interface</firstterm>
   (<acronym>SPI</acronym>) gives writers of user-defined
   <acronym>C</acronym> functions the ability to run
-  <acronym>SQL</acronym> commands inside their functions.
+  <acronym>SQL</acronym> commands inside their functions or procedures.
   <acronym>SPI</acronym> is a set of
   interface functions to simplify access to the parser, planner,
   and executor. <acronym>SPI</acronym> also does some