Will call:
void sail_branch_reached(int branch_id, char *source_file, int l1, int c1, int l2, int c2);
on each branch caused by a match or if statement in the source code
For each branch that is taken, will call:
void sail_branch_taken(int branch_id, char *source_file, int l1, int c1, int l2, int c2)
Every branch gets a unique identifier, and the functions are called with
the source file location and line/character information for the start
and end of each match case or then/else branch. sail_branch_reached is
given the location info for the whole match statement.