Pod::Simple::XHTML: better fallback when HTML::Entities isn't installed

This commit changes the default set of escaped characters in the
fallback code to be the same as in HTML::Entities.

Fixes #188

Author: xenu

lib/Pod/Simple/XHTML.pm

@@ -70,7 +70,8 @@ sub encode_entities {
       $ents =~ s,(?<!\\)([]/]),\\$1,g;
       $ents =~ s,(?<!\\)\\\z,\\\\,;
   } else {
-      $ents = join '', keys %entities;
+      # the same set of characters as in HTML::Entities
+      $ents = '^\n\r\t !\#\$%\(-;=?-~';
   }
   my $str = $_[0];
   $str =~ s/([$ents])/'&' . ($entities{$1} || sprintf '#x%X', ord $1) . ';'/ge;