mtree violations should be debug info, should not be fatal errors

[Anders F Björklund]

Weissmann Markus wrote:

> we've documented the should-be state of the layout of the 
> ports-filesystems years ago already - see porthier(7); if ports fail 
> because of this right now, it is most likely either because our 
> implementation is faulty or the port is buggy.

Seems like "src" is missing from the porthier/mtree, this breaks the 
"port rpm/srpm" targets and the "rpm/rpm-devel" ports. I'd prefer if it 
could be added to the hier, rather than having to make 
/opt/local/src/macports an exception from the rules ?

--anders