[BUG FIX] Compare difference to 0 for equality. (#272)

In bug_79_double_complex, the bitwise comparison `res1 .ne. res2`
returns true on some archs (i586) though `res1` and `res2` are equal
upto double precision. Instead compare the absolute value of their
difference to double precision 0 which works on all archs. Fixes #269.

Co-authored-by: Atri Bhattacharya <A.Bhattacharya@uliege.be>

TESTS/bug_79_double_complex.f

@@ -217,7 +217,12 @@ c           %----------------------------------%
             go to 9000
          end if
  9000 continue
-      if (res1 .ne. res2) then
+c     Compare difference to double precision 0 instead of using
+c     bitwise comparison operator .ne.
+      if (abs(res1 - res2) > 0.0D+0) then
+         write(6,'(a,e24.16,a,e24.16,a,e24.16)')
+     &        "ERROR res1 (", res1, " ) not equal to res2 (", res2,
+     &        " ); difference = ", res1 - res2
          stop 1
       end if
       end