Bug 22508

It would be nice if when a ProxyClassLoader is
asked to load some class which could be found in
more than one parent classloader, a warning was
logged. Typically this would mean that two
versions of a library L coexist at once in the VM
- say, L1 and L2 - and some module accidentally
depends on both - say, M1 on L1, M2 on L2, M3 on
M1 and M2 - and an attempt is made to load a class
in the L namespace from M3. In this case the
result is arbitrary, which could be dangerous.

It may be that the warning can only be logged in
the case that both L1 and L2 have done some
classloading in the package in question by the
time that M3 tries to load from that package
(because of the package shortcut optimizations in
ProxyClassLoader).