Converts a data field as it stored in the database file into a bcd string. The string will not be longer
than 20 chars including the final 0. It contains only the characters `+', `-', `0-9', and `.'. You
should use this function instead of accessing the data directly.
data points to the start of the data field in the record. It must be calculated by summing up all field
length before the field to operate on and add it to the base pointer of the record. len is the number of
digits after the decimal point.
The function allocates memory for the string returned in *value. This memory has to be freed by the
application.
Note:
This function is deprecated and obsolete if PX_retrieve_record(3) is used.