Reinstate -DNO_SECUREZEROMEMORY for the Coverity build.

In commit 188e2525c I removed it from Winelib builds in general on the
grounds that Winelib had acquired that function. But now that I come
to try a Coverity build, I find that that is still one Winelib build
that does fail if I call SecureZeroMemory.

Buildscr.cv

@@ -25,7 +25,7 @@ enddelegate
 # Windows scanner for download).
 delegate covscan32wine
   in putty do tar xzvf cov-int.tar.gz
-  in putty/windows do cov-build --dir ../cov-int make -f Makefile.mgw CC=winegcc RC=wrc XFLAGS=-DCOVERITY
+  in putty/windows do cov-build --dir ../cov-int make -f Makefile.mgw CC=winegcc RC=wrc XFLAGS="-DCOVERITY -DNO_SECUREZEROMEMORY"
   in putty do tar czvf cov-int.tar.gz cov-int
   return putty/cov-int.tar.gz
 enddelegate