Modified the library version to indicate ABI/API backwards incompatibility

Release 2.9.0 - June 27, 2022

- Corrected library versioning numbers to indicate API/API incompatibility
  - libframecpp8 11:0:0
  - libframecpp 15:0:0
- Corrected default slope value for version 8 FrAdcData (closes computing/ldastools/LDAS_Tools#114)
- Code cleanup for SWIG compilation
- Corrected type for FrSimEvent::parameters (REAL_4 => REAL_8)
- Modified FrSimEvent time type to be GPSTime (consitent with FrEvent)
- Modified FrameCPP::Common::AppendComment to prevent STRING overflow (closes computing/ldastools/LDAS_Tools#138)
- Modified FrameCPP::Common::AppendComment to prevent copying of duplicates to STRING (closes computing/ldastools/LDAS_Tools#140)
- Fixed issue with calculating cksums for files that were larger than 4G (closes computing/ldastools/LDAS_Tools#137)