rsaenh: fix bugs in RSAENH_CPAcquireContext and RSAENH_CPGetProvParam

[Maarten Lankhorst]

Mounir IDRASSI schreef:
> We have found few bugs in the MS Enhanced CSP implementation in wine
> (rsaenh.dll) and you'll find attached a patch that corrects them.
Hello Mounir,

Bug fixes are always welcome in wine.
But fixing bugs is one thing, but it is also very recommended to add
tests to verify the behavior is correct. I don't see any tests added in
this patch so it is hard to verify. Please also update dlls/rsaenh/tests
with some simple tests if possible, it will make it more likely that the
code will be accepted.

Cheers,
Maarten