Change the compiler's big integer library to use libTomMath

This now replaces Bill's crappy big int implementation

src/libtommath/mp_init.c

@@ -0,0 +1,23 @@
+#include "tommath_private.h"
+#ifdef MP_INIT_C
+/* LibTomMath, multiple-precision integer library -- Tom St Denis */
+/* SPDX-License-Identifier: Unlicense */
+
+/* init a new mp_int */
+mp_err mp_init(mp_int *a)
+{
+   /* allocate memory required and clear it */
+   a->dp = (mp_digit *) MP_CALLOC((size_t)MP_DEFAULT_DIGIT_COUNT, sizeof(mp_digit));
+   if (a->dp == NULL) {
+      return MP_MEM;
+   }
+
+   /* set the used to zero, allocated digits to the default precision
+    * and sign to positive */
+   a->used  = 0;
+   a->alloc = MP_DEFAULT_DIGIT_COUNT;
+   a->sign  = MP_ZPOS;
+
+   return MP_OKAY;
+}
+#endif