This patch allows configurable formatting of date/time as text in
Excel output.

To enforce use of text format in Excel charts, set the
REPORTS_EXCEL_CHART_TEXT directive to a comma separated list of time
intervals to be formatted as text. The following intervals are
allowed: "year", "month", "week", "day", and "hms". "hms" covers all
intervals equal to or shorter than one hour.

If e.g. the days and shorter intervals are to be displayed as text,
include the following line in /etc/opt/openit/openit.cfg:

REPORTS_EXCEL_CHART_TEXT  day,hms

Note that "hms" is set by default (and could be skipped in the above
example). Also note that there must be no space characters in the
comma separated list.