Common: Require explicit handle validation

Using operator bool() hid ambiguity when handle was polymorfic with
bool. Using operator!() reqired !! to test for validity which results in
awkward code.

Signed-off-by: Simon Rozman <simon@rozman.si>

include/WinStd/BCrypt.h

@@ -125,7 +125,7 @@ namespace winstd
             if (this != std::addressof(h)) {
                 if (m_h != invalid)
                     free_internal();
-                if (h)
+                if (h.valid())
                     duplicate_internal(h);
                 else
                     m_h = invalid;

include/WinStd/COM.h

@@ -1665,7 +1665,7 @@ namespace winstd
             };
             sa = SafeArrayCreate(VT_VARIANT, _countof(dim), dim);
         }
-        if (!sa)
+        if (!sa.valid())
             throw std::bad_alloc();
 
         assert(SafeArrayGetElemsize(sa) == sizeof(VARIANT));