Fixed so that wiki.listLinks() returns external as well as internal links.

Fixed so that wiki.listLinks() returns external as well as internal links.

Since the external links aren't currently stored in the link database,
we need to scan the page text for the links.  We might as well pull the
internal links out from the same scan.  (Commented out the old code
which queries the link db.)

Also fixed a couple bugs/features:
 o wiki.listLinks() was listing backlinks not outgoing links.
 o When urlencoding short strings we only really need to encode
   the ascii control characters (which aren't allowed in XML 1.0 :-/)

git-svn-id: svn://svn.code.sf.net/p/phpwiki/code/trunk@2346 96ab9672-09ca-45d6-a79d-3d69d39ca109