Log Message:
Update mathomatic to 12.7.1.

Changes:
- Remove GPL preamble in "primes/*.c", so everything is LGPL.
- Allow entering "e#" and "i#" as "e" and \ 
"i". Display "e", "i", and "pi" as
  "e#", "i#", and "pi#".
- Require a space between command and command line, so variables don't get
  confused with commands. This is a bug fix.
- Added a directory named "hard_stuff".
- Fixed error in "tests/finance.in".