Package/Device for a component with duplicated pins
You should solder all the pins and use both in and both out pins for the connection to your traces on the PCB. Combining multiple adjacent pins, especially on thin-pitch ICs, is done to allow for better thermal and inductive behaviour of the respective connection.

A Quote from the L79L datasheet:


  Our SO-8 package used for Voltage Regulators is modified inter nally to have pins 2, 3, 6 and 7 electrically communed to the die attach flag. This particular frame decreases the total thermal resistance of the package and increases its ability to dissipate power when an appropriate area of copper on the printed circuit board is available for heat-sinking. The external dimensions are the same as for the standard SO-8.