Log Message:
Update mathomatic 11.6.

Changes:
  - Many minor improvements made, none of which are worth mentioning by
    themselves.
  - Fixed all message strings with a variable listed in them.
  - Added iteration option to calculate command.
  - Trimmed set command of fat.  Unnecessary messages removed.
  - Removed all occurrences of "usage_flag".
  - Usage info is now displayed everytime a command returns with error.
  - Allow parsing of hexadecimal constants.  Preceed hex numbers with
    "0x".
  - There may be parsing bugs.  Systems using older versions of the GNU
    libraries (specifically strtod(3)) will not allow hexadecimal input.
  - Added limit command.
  - Trapped 0^(negative number).  It previously produced junk.
  - Allow solve routine to produce infinity as an answer.
  - Some commenting and fixing done to solve routine.