ModSim: Added assignment 3.

modsim/ass3/diff.c

+#include <stdlib.h>
+#include <stdio.h>
+
+int main(void) {
+
+
+    return 0;
+}

modsim/ass3/func_ptr.h

+#ifndef FUNC_PTR_H
+#define FUNC_PTR_H
+
+typedef double (*func_ptr)(double t);
+typedef double (*diff_ptr)(double t, func_ptr y);
+
+#endif