Change the compiler's big integer library to use libTomMath

This now replaces Bill's crappy big int implementation

src/libtommath/mp_div_d.c

@@ -0,0 +1,84 @@
+#include "tommath_private.h"
+#ifdef MP_DIV_D_C
+/* LibTomMath, multiple-precision integer library -- Tom St Denis */
+/* SPDX-License-Identifier: Unlicense */
+
+/* single digit division (based on routine from MPI) */
+mp_err mp_div_d(const mp_int *a, mp_digit b, mp_int *c, mp_digit *d)
+{
+   mp_int  q;
+   mp_word w;
+   mp_err err;
+   int ix;
+
+   /* cannot divide by zero */
+   if (b == 0u) {
+      return MP_VAL;
+   }
+
+   /* quick outs */
+   if ((b == 1u) || mp_iszero(a)) {
+      if (d != NULL) {
+         *d = 0;
+      }
+      if (c != NULL) {
+         return mp_copy(a, c);
+      }
+      return MP_OKAY;
+   }
+
+   /* power of two ? */
+   if (MP_HAS(MP_DIV_2) && (b == 2u)) {
+      if (d != NULL) {
+         *d = mp_isodd(a) ? 1u : 0u;
+      }
+      return (c == NULL) ? MP_OKAY : mp_div_2(a, c);
+   }
+   if (MP_HAS(MP_DIV_2D) && MP_IS_2EXPT(b)) {
+      ix = 1;
+      while ((ix < MP_DIGIT_BIT) && (b != (((mp_digit)1)<<ix))) {
+         ix++;
+      }
+      if (d != NULL) {
+         *d = a->dp[0] & (((mp_digit)1<<(mp_digit)ix) - 1uL);
+      }
+      return (c == NULL) ? MP_OKAY : mp_div_2d(a, ix, c, NULL);
+   }
+
+   /* three? */
+   if (MP_HAS(S_MP_DIV_3) && (b == 3u)) {
+      return s_mp_div_3(a, c, d);
+   }
+
+   /* no easy answer [c'est la vie].  Just division */
+   if ((err = mp_init_size(&q, a->used)) != MP_OKAY) {
+      return err;
+   }
+
+   q.used = a->used;
+   q.sign = a->sign;
+   w = 0;
+   for (ix = a->used; ix --> 0;) {
+      mp_digit t = 0;
+      w = (w << (mp_word)MP_DIGIT_BIT) | (mp_word)a->dp[ix];
+      if (w >= b) {
+         t = (mp_digit)(w / b);
+         w -= (mp_word)t * (mp_word)b;
+      }
+      q.dp[ix] = t;
+   }
+
+   if (d != NULL) {
+      *d = (mp_digit)w;
+   }
+
+   if (c != NULL) {
+      mp_clamp(&q);
+      mp_exch(&q, c);
+   }
+   mp_clear(&q);
+
+   return MP_OKAY;
+}
+
+#endif