fix FLT_ROUNDS to reflect the current rounding mode

Implemented as a wrapper around fegetround introducing a new function
to the ABI: __flt_rounds. (fegetround cannot be used directly from float.h)

src/fenv/__flt_rounds.c

@@ -0,0 +1,19 @@
+#include <float.h>
+#include <fenv.h>
+
+int __flt_rounds()
+{
+	switch (fegetround()) {
+#ifdef FE_TOWARDZERO
+	case FE_TOWARDZERO: return 0;
+#endif
+	case FE_TONEAREST: return 1;
+#ifdef FE_UPWARD
+	case FE_UPWARD: return 2;
+#endif
+#ifdef FE_DOWNWARD
+	case FE_DOWNWARD: return 3;
+#endif
+	}
+	return -1;
+}