Change the compiler's big integer library to use libTomMath

This now replaces Bill's crappy big int implementation

src/libtommath/mp_cmp.c

@@ -0,0 +1,21 @@
+#include "tommath_private.h"
+#ifdef MP_CMP_C
+/* LibTomMath, multiple-precision integer library -- Tom St Denis */
+/* SPDX-License-Identifier: Unlicense */
+
+/* compare two ints (signed)*/
+mp_ord mp_cmp(const mp_int *a, const mp_int *b)
+{
+   /* compare based on sign */
+   if (a->sign != b->sign) {
+      return mp_isneg(a) ? MP_LT : MP_GT;
+   }
+
+   /* if negative compare opposite direction */
+   if (mp_isneg(a)) {
+      MP_EXCH(const mp_int *, a, b);
+   }
+
+   return mp_cmp_mag(a, b);
+}
+#endif