Log Message:
update to 1.1.3
changes:
* Added support for constants e, log2(e), log10(e), ln(2), ln(10), pi,
  pi/2, pi/4, 1/pi, 2/pi, 2/sqrt(pi), sqrt(2) and sqrt(1/2).
* Fixed bug with using global instead of evaluator specific symbol table
  variable in evaluator_get_variables() function.