Changes to SeBa version 1.0
C version
Changes to SeBa version 2.0
C++ version
Changes to SeBa version 3.0
Implementation to Starlab version 3.0
Changes to SeBa version 3.1
implementation of class constants 
Changes to SeBa version 3.3

- Orbital timestep implemented in double_star::determine_dt.
- Core mass determination for giants.
- Core radus for giants equals radius of helium star .
- structure double_star::recursive..
- timestep decrement to end of stellar phase.
- double_star::set_donor_timescale() in recursive::recursive...
- Carbon cores for helium_stars.
- Stellar wind for helium_stars and helium_giants.
- Stellar wind for main_sequence stars and giants.
- Enhanced stellar wind for massive main_sequence stars.
- Stellar wind for wolf_rayet stars.
- Core-mass and radius altered in wolf_rayet stars.
- Low-mass helium stars turn into white dwarfs directly.
- Mass not accreted by compact object leaves binary with
  specific angular momentum parameterized as for other stars,
- single_star::update_relative_mass() mplemented in ::add_mass_to_accretor() 
- stellar rejuvenation made Hydrogen/Helium dependent.
- single_star::adjust_accretor_radius() removed.
- main_sequence donors enlarged in transfer on dynamic and thermal timescale.
- relative mass of low-mass main_sequence donors reduced upon mass loss.
- ::common_envelope and ::spiral_in changed.
- ::double_spiral_in() added for merging contact binaries.
- Tidal instability depends not on gyration radius.
- ::gyration_radius() added to single_star.
- Thermal and adiabatic resonce functions for stars adjusted.
- double_star::zeta() altered.
- mass transfer type parametrized.
- donor_timescale is now also member of double_hist::.
- nuclear timescale for giants is made shorter.
- double_star::mdot_according_to_roche_radius_change changed.
- amount of mass lost in spiral in increased for mergers.
- relative_mass and relative_age determination of mergers altered.
- added function: single_star::add_mass_to_core();
- single_star::reduce_donor_mass() is now ::reduce_mass().
- Black hole mass made relative_mass dependent.
- (Core) mass limits for black_ hole and neutron_star changed. 
- helium_giants receive own ::adjust_next_update_age().
  This function shoud only be called in the constructor.
- age of newly created helium_star:: is larger for horizontal_branch:: and 
  super_giant:: progenitors.
- Stars with M > 20.97184...Msun do not ascend the sub_giant branch
  but become directly a horizontal branch star.
- temperature is now in Kelvin, was in units of 1000 Kelvin.
- Giant luminosities altered according to Tout et al. 97.
- nuclear timescale for main-sequence stars reformulated.
- single_star::mass_ratio_mdot_limit() removed.
- wolf_rayet stars changes into helium_star when mass drops below
  minimum_helium_star_mass
- minimal_timestep is used in mass transfer.
- dt is set at beginning op double_star::recursive..
