Visual Studio: fix feraiseexcept test failure

We have a test that checks that our own implementation of feraiseexcept
triggers an assertion failure when a non-zero argument is given.  This test
now fails since Visual Studio has a macro for feraiseexcept.

This commit uses #undef to avoid Visual Studio's macro.

Author: kroening

regression/cbmc-library/feraiseexcept-01/main.c

@@ -1,6 +1,10 @@
 #include <assert.h>
 #include <fenv.h>
 
+// Avoid using a macro defined by the library,
+// we want to test our own implementation.
+#undef feraiseexcept
+
 int main()
 {
   int exceptions;