fehler76: assertion when converting float constant to int

fix source of fehler74 and fehler75.

[r15740]

ir/be/test/fehler74.c

+/*$ -std=c99 $*/
+
 #include <stdio.h>
 #include <math.h>
 

ir/be/test/fehler75.c

@@ -8,4 +8,5 @@ long long k(long long a)
 int main(void)
 {
 	printf("%lld\n", k(0x80000000LL));
+	return 0;
 }

ir/be/test/fehler76.c

+int main(void)
+{
+	float f = 1223432e3;
+	long  l = f;
+	printf("long %ld float %f\n", l, f);
+	return 0;
+}