Version 0.7.3 (2007.03.08):
	* added: the program shows some kind of errors itself
	* added: checking whether an user has inserted a correct value of a variable or a function
	* fixed: navigation from the keyboard
	* changed: the esc key selects the entire input text now (in the input edit)
	* added: a test when the program is being starded which checks if the coordinates of the
      main window actually pointing at the valid area (for example when someone took
      his configuration file into a new computer and the new computer has a smaller screen)

Version 0.7.2 (2007.02.28):
	* added buttons Sgn and Mod
	* the button 'err' is active when there's actually an error now
	* added buttons: ASin, ACos, ATan, ACTan
	* fixed: the program didn't save the current language into the configuration file
	* fixed: the second thread didn't read the main window correctly and it caused
	  small problems when an user was typing into the first edit control

Version 0.7.1 (2007.02.08):
	* added a button 'err' (error) on the first tab
	* the input edit can have 2048 characters now
	* added remembering the vertical size into the config file
	* fixed a problem with the 'tab' key
	* added a message 'Calculating...' when an user clicks on the 'err' button
	  during calculating something