[tex-live] dvipdfmx depends on system libpng

[Karl Berry]

    it's this
    code which caused a problem (and lacks the proper -I's):

Oh.  It's making the dependencies.  I didn't notice that. 

Well, it will take some effort to figure out how to affect the compile
flags for doing that.  Meanwhile, it shouldn't make any difference to
the actual binary, since the right flags were used there.  So I think
it's ok to proceed.