RESEND CryptEnumProviders a->w cleanup and tests

[James Hawkins]

Hi,

I'm not sure whether these two patches were misplaced or they were
considered not good enough to be committed, but I've included the
patches now.  I spent a lot of time hunting down any bugs in my
unicode version of CryptEnumProviders as well as writing tests of its
functionality.  All the tests succeed except for one (wrong error
message being sent back from undersized buffer) but that bug is a part
of the original CryptEnumProviders as well and as soon as this patch
can be committed, I can submit a fix for that bug.  If there turns out
to be problems with the patch, or the style is not up to par with wine
coding standards, please let me know, because I really want to get
this committed.