Improve fix from PR3924 (#3941)

* compare denominator against DBL_MIN rather than a somewhat arbitrary small number near it

Author: martin-frbg

lapack/getf2/getf2_k.c

@@ -37,6 +37,7 @@
 /*********************************************************************/
 
 #include <stdio.h>
+#include <float.h>
 #include "common.h"
 
 static FLOAT dp1 =  1.;
@@ -100,7 +101,7 @@ blasint CNAME(blas_arg_t *args, BLASLONG *range_m, BLASLONG *range_n, FLOAT *sa,
       temp1 = *(b + jp);
 
       //if (temp1 != ZERO) {
-	if (fabs(temp1) > 1.e-305) {    
+	if (fabs(temp1) >= DBL_MIN ) {
 	temp1 = dp1 / temp1;
 
 	if (jp != j) {

lapack/getf2/zgetf2_k.c

@@ -37,6 +37,7 @@
 /*********************************************************************/
 
 #include <stdio.h>
+#include <float.h>
 #include "common.h"
 
 double fabs(double);
@@ -106,7 +107,7 @@ blasint CNAME(blas_arg_t *args, BLASLONG *range_m, BLASLONG *range_n, FLOAT *sa,
       temp2 = *(b + jp * 2 + 1);
 
   //    if ((temp1 != ZERO) || (temp2 != ZERO)) {
-	if ((fabs(temp1) > 1.e-305) || (fabs(temp2) > 1.e-305)) {
+	if ((fabs(temp1) >= DBL_MIN) && (fabs(temp2) >= DBL_MIN)) {
 
 	if (jp != j) {
 	  SWAP_K(j + 1, 0, 0, ZERO, ZERO, a + j * 2, lda,