POSIX: removed spurious double literal suffix

src/OSspecific/POSIX/POSIX.C

@@ -530,11 +530,11 @@ double Foam::highResLastModified(const fileName& name)
     {
         return
             fileStatus.status().st_mtime
-          + 1e-9d*fileStatus.status().st_atim.tv_nsec;
+          + 1e-9*fileStatus.status().st_atim.tv_nsec;
     }
     else
     {
-        return 0.0;
+        return 0;
     }
 }