Using a more aggressive test for resolving pattern equations ?n = ?p:
test pattern-unification after restriction of the evars so as to
succeed earlier (no observational changes however in the examples at my
disposal).
Fixing orientation of postponed subtyping problems.
In the case of conversion, postponing by preserving the
initial orientation.

Was wrong from its initial version in Jan 2014, but was not visible
because evar-evar subtyping was approximated by evar-evar conversion.

Thanks to Enrico for a very short example highlighting the problem. In
particular, this fixes Ergo.