Session active and start is different depending on version of PHP.
Avoid session already active warnings by using PHP functions rather than globals.
updated comment on wpsc_core_load_session.
adjusted booleans returns to return expression result.
added @since 3.8.14 in the doc block.
fixed whitespace.
whitespace on both sides of logical operators
Merge pull request #836 from JeffPyeBrook/session-start

Session active and start may behave differently depending on version of PHP.