This function will change the text of a Document object to the text
specified by the "Text" parameter. The new text is asumend to be
encoding according to the UTF-8 encoding. If the text is stored using a
different encoding, the caller must use CDM_ExternalToUtf in order to
convert the text to UTF. CDM will internally alocate a new memory area
to store the given text.
Return Value:
The return value from this function will be a standart Tcl completion
code (of type int) with one of the values TCL_OK and TCL_ERROR. If an
error occurs, the return value will be TCL_ERROR and an error message
describing the error will be left at the current Tcl interpreter
(CDM_Interp).