Log Message:
Update txt2html to 2.51.

pkgsrc changes:
 * set LICENSE=${PERL5_LICENSE}
 * update dependencies (Getopt::Long is a part of CORE since perl-5, so drop it)

Revision history for txt2html
=============================

2.51 Sun 4th March 2008
	- fixed bug with underscores in links
	- fixed docs about escape_chars (should be escapechars)
	- fixed docs about DOCTYPE

2.50 Sat 22nd December 2007
	- fixed bug with formatting and punctuation
	- removed old reference-to-an-array argument method
	- made --xhtml true by default (used to be false)
	- moved the debugging options to global variables

2.46 Fri 9th November 2007
	- updated docs on custom_heading_regexp
	- fixed bug with xhtml output
	- documented all undocumented functions