Data::Dumper patch

Hello.

Patch to make Data::Dumper compile on older Perl's.
my_sprintf is available only on 5.10 and cannot be supported by
ppport.h (requires probe). Also added
#define NEED_my_snprintf

-- 
Alexandr Ciornii, http://chorny.net

• Data::Dumper patch by Alexandr Ciornii
• Re: Data::Dumper patch by Marcus Holland-Moritz
• Re: Data::Dumper patch by Dave Mitchell
• Re: Data::Dumper patch by Dave Mitchell
• Re: Data::Dumper patch by Rafael Garcia-Suarez