Log Message:
Changes 0.7.1:
* Only use unicode character if available in the used font
  Fixes plus sign not displayed correctly in keypad, and wide keypad
* Do not round exact integers not in exponential format.
  Fixes display of large numbers in non-decimal number bases * Fix crash on \ 
systems, such as amd64, where size_t is not long int
* Do not update plot data when not changed
* Rearrange plot dialog and make x variable separate for each plot
  function
* Generate vector function
* Fix some cases with nested trigonometric functions by adding
  option to set default angle unit to none, to allow angle unit in argument
* Try with assumptions set to unknown in solve function if not successful
* Be more picky in comparisons with units
* Fix comparison of unit with unknown
* Fix 0.5!