- Updates libpng to 1.6.37 (from 1.6.23)
Note: Seems svn can't merge it automatic when a folder was removed and readded with same name.
Easier to update libs by deleting all files - copying new ones over and then check svn stat for differences
and resolve them manually.
git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@6171 dfc29bdd-3216-0410-991c-e03cc46cb475
