Log Message:
Update mathomatic to 12.5.19.

Changes:
6/18/06 - Made entering "a=b=c" give an error, instead of just \ 
ignoring "c".
6/18/06 - Made "inf" an invalid variable, should be a constant only.
6/18/06 - Improved prompting for a variable.
6/18/06 - Mathomatic now properly removes all trailing spaces from input.
6/21/06 - Beautified the Mathomatic manuals.
6/23/06 - Remove semicolon from output of "code python" command.
6/27/06 - Add "tests/trig.in" to the tests.
6/29/06 - Allow typing "?" as a quick way to get help.