Change the compiler's big integer library to use libTomMath

This now replaces Bill's crappy big int implementation

src/libtommath/s_mp_log_d.c

@@ -0,0 +1,65 @@
+#include "tommath_private.h"
+#ifdef S_MP_LOG_D_C
+/* LibTomMath, multiple-precision integer library -- Tom St Denis */
+/* SPDX-License-Identifier: Unlicense */
+
+static mp_word s_pow(mp_word base, mp_word exponent)
+{
+   mp_word result = 1u;
+   while (exponent != 0u) {
+      if ((exponent & 1u) == 1u) {
+         result *= base;
+      }
+      exponent >>= 1;
+      base *= base;
+   }
+
+   return result;
+}
+
+int s_mp_log_d(mp_digit base, mp_digit n)
+{
+   mp_word bracket_low = 1uLL, bracket_high = base, N = n;
+   int ret, high = 1, low = 0;
+
+   if (n < base) {
+      return 0;
+   }
+   if (n == base) {
+      return 1;
+   }
+
+   while (bracket_high < N) {
+      low = high;
+      bracket_low = bracket_high;
+      high <<= 1;
+      bracket_high *= bracket_high;
+   }
+
+   while (((mp_digit)(high - low)) > 1uL) {
+      int mid = (low + high) >> 1;
+      mp_word bracket_mid = bracket_low * s_pow(base, (mp_word)(mid - low));
+
+      if (N < bracket_mid) {
+         high = mid ;
+         bracket_high = bracket_mid ;
+      }
+      if (N > bracket_mid) {
+         low = mid ;
+         bracket_low = bracket_mid ;
+      }
+      if (N == bracket_mid) {
+         return mid;
+      }
+   }
+
+   if (bracket_high == N) {
+      ret = high;
+   } else {
+      ret = low;
+   }
+
+   return ret;
+}
+
+#endif