strlst/spngfx: example implementation of my png lib

strlst be18d25b81 old changes		%!s(int64=3) %!d(string=hai) anos
..
test	be18d25b81 old changes	%!s(int64=3) %!d(string=hai) anos
testall	0f0bb2528b added way to apply image kernels	%!s(int64=5) %!d(string=hai) anos