Log Message:
Update mathomatic to 12.4.3.

Changes:
 - Allow larger fractions.
 - Doubled the default max expression size and memory requirements are
   now 20 megabytes.
 - Added ability to set the number of partitions when using the
   nintegrate command.
 - Some code and messages cleanup.
 - Fixed bug in nintegrate command (wrong number of function parameters).
 - Improved solve routine.
 - Update to "primes/matho-around.c".