Fix floating point number comparisons in testsuite/libffi.call/float[123].c.

Rewrite the checks for approximate equality of floating point return
values to be in the form "fabs(a - b) < EPS" instead of just
"a - b < EPS".

testsuite/libffi.call/float1.c

@@ -8,6 +8,8 @@
 #include "ffitest.h"
 #include "float.h"
 
+#include <math.h>
+
 typedef union
 {
   double d;
@@ -47,7 +49,7 @@ int main (void)
 
   /* These are not always the same!! Check for a reasonable delta */
 
-  CHECK(result[0].d - dblit(f) < DBL_EPSILON);
+  CHECK(fabs(result[0].d - dblit(f)) < DBL_EPSILON);
 
   /* Check the canary.  */
   for (i = 0; i < sizeof (double); ++i)