add some f2c runtime functions, remove exception, avoid name conflict with libgfortran

lib/linalg/i_lmp_dnnt.cpp

@@ -0,0 +1,12 @@
+
+#include "lmp_f2c.h"
+
+#undef abs
+#include <cmath>
+
+extern "C" {
+integer i_lmp_dnnt(doublereal *x)
+{
+    return (integer)(*x >= 0. ? floor(*x + .5) : -floor(.5 - *x));
+}
+}