IDL Routine: LANCZOS_BANDPASS

If you send me <air_jlin@yahoo.com> your email address, I'll let you know of any major bugs that are found in this library.

8 Jun 2002: Change made to Zero_Endpts keyword. Prior to this change, if this keyword was true, the endpoints would be set to zero, and the timeseries then filtered. If the Detrend was true, then retrending would occur with respect to the zero values at the endpoints. With this change, after filtering, the new filtered timeseries would have endpoints of the original values of the timeseries.