fix overflow in several advapi32 crypt functions hidden by broken WideCharToMultiByte

[James McKenzie]

Christoph von Wittich wrote:

As Dmitry wrote about this, I will add the comment that this does not
look like the proper way to fix this problem.  The proper way is to keep
the pointer from overflowing in the first place and that would be to
place a check where it is set and updated to either go negative (which
should not be allowed) or to be incremented past INT_MAX.  This can be
implemented in several different ways, and since I have not looked at
the code, I could not make a proper suggestion but would suggest that
the pointer be checked before incrementing and after setting.

James McKenzie