Changed the behavior of dw_html_new() to return NULL on failure like the documentation indicates... Instead of creating a text widget with an error message. This error message is now sent to the console. This allows programs to be able to gracefully handle the failure to create the HTML widget. Also updated the dwtest program to create a text widget in a similar fashion on failure. Also updated the dw_calendar_* comments to no longer be unsupported on OS/2.

# Set these here to change the version for all platforms
DW_MAJOR_VERSION=2
DW_MINOR_VERSION=2