Update LibTomMath to 1.2.0 (#84)

* update C files

* update other files

* update headers

* update makefiles

* remove mp_set/get_double()

* use ltm 1.2.0 API

* update ltm_desc

* use bundled tommath if system-tommath is too old

* XMALLOC etc. were changed to MP_MALLOC etc.

libtommath/bn_s_mp_get_bit.c

@@ -0,0 +1,21 @@
+#include "tommath_private.h"
+#ifdef BN_S_MP_GET_BIT_C
+
+/* LibTomMath, multiple-precision integer library -- Tom St Denis */
+/* SPDX-License-Identifier: Unlicense */
+
+/* Get bit at position b and return MP_YES if the bit is 1, MP_NO if it is 0 */
+mp_bool s_mp_get_bit(const mp_int *a, unsigned int b)
+{
+   mp_digit bit;
+   int limb = (int)(b / MP_DIGIT_BIT);
+
+   if (limb >= a->used) {
+      return MP_NO;
+   }
+
+   bit = (mp_digit)1 << (b % MP_DIGIT_BIT);
+   return ((a->dp[limb] & bit) != 0u) ? MP_YES : MP_NO;
+}
+
+#endif