dstlen < 0 for MultiByteToWideChar / WideChatToMultiByte

[Michael Stefaniuc]

Hello Detlef,

although Smatch could have handled the task too of finding places where 
Wine passes -1 as destlen to MultiByteToWideChar / WideChatToMultiByte 
this can be done with the C compiler too. Please see the attached patch.

This solution doesn't finds more occurrences that you have found and 
patched already. But this is really only the stuff that the compiler can 
figure out at compile time. It has no chance at all to catch stuff like

void foo(int bar)
{
     int dstlen = -1;

if (bar)
         dstlen = 10;

MultiByteToWideChar(a, b, c, d, e, dstlen)
}

Those can't be found by a grep either and I think that's why Alexandre 
is reluctant to apply your patches.

bye
    michael