Tidy up and refactor plperl.c.

- Changed MULTIPLICITY check from runtime to compiletime.
    No loads the large Config module.
- Changed plperl_init_interp() to return new interp
    and not alter the global interp_state
- Moved plperl_safe_init() call into check_interp().
- Removed plperl_safe_init_done state variable
    as interp_state now covers that role.
- Changed plperl_create_sub() to take a plperl_proc_desc argument.
- Simplified return value handling in plperl_create_sub.
- Changed perl.com link in the docs to perl.org and tweaked
    wording to clarify that require, not use, is what's blocked.
- Moved perl code in large multi-line C string literal macros
    out to plc_*.pl files.
- Added a test2macro.pl utility to convert the plc_*.pl files to
    macros in a perlchunks.h file which is #included
- Simplifed plperl_safe_init() slightly
- Optimized pg_verifymbstr calls to avoid unneeded strlen()s.

Patch from Tim Bunce, with minor editing from me.

doc/src/sgml/plperl.sgml

@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/plperl.sgml,v 2.71 2009/11/29 03:02:27 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/plperl.sgml,v 2.72 2010/01/09 02:40:50 adunstan Exp $ -->
 
  <chapter id="plperl">
   <title>PL/Perl - Perl Procedural Language</title>
@@ -14,7 +14,7 @@
   <para>
    PL/Perl is a loadable procedural language that enables you to write
    <productname>PostgreSQL</productname> functions in the 
-   <ulink url="http://www.perl.com">Perl programming language</ulink>.
+   <ulink url="http://www.perl.org">Perl programming language</ulink>.
   </para>
 
   <para>
@@ -313,7 +313,8 @@ SELECT * FROM perl_set();
 use strict;
 </programlisting>
    in the function body.  But this only works in <application>PL/PerlU</>
-   functions, since <literal>use</> is not a trusted operation.  In
+   functions, since the <literal>use</> triggers a <literal>require</>
+   which is not a trusted operation.  In
    <application>PL/Perl</> functions you can instead do:
 <programlisting>
 BEGIN { strict->import(); }