lal/src/date/Date.h: remove #include of LALStdLib
Completes the removal of the LALStatus structure from lal's date package (already no code in the package uses the symbol, but the header files still suck in the LALStatus error machinery).
API Changes and Justification
Backwards Compatible Changes
- This change introduces no API changes
- This change adds new API calls
Backwards Incompatible Changes
- This change modifies an existing API
- This change removes an existing API
Because this modifies header files the API is changed, but not the ABI, and not the API in a way that matters to the date package itself. As usual, there is code that has been relying on the date package's header files to #include symbols that other code requires, so the patch needs to add a few #include statements here and there, but only in the lal library. No code outside of lal proper is affected.