Log Message:
Update mathomatic to 12.6.1.

Major changes:
- Added alternate command names.
- Don't allow imaginary numbers in integer only expressions.
- Made poly_gcd_simp() do its job in one pass.
- Add "set autosolve" option.
- Make entry of "=(expression)" into "0=(expression)", \ 
instead of being an
  error.
- Add fraction command.
- Made simplification default to polynomial simplify.
- "replace constants" command now approximates constants with roots.
- Fixed a floating point accuracy issue recently introduced.
- Other bug fixes and improvements.