Locate returns where the generated line and column, from 1, came from: the
last segment at or before the column. A column of 0 takes the line's first
segment. It returns false for a line with no segment there.
type Position struct {
// Source is the file as the map names it, relative to the map's// directory unless the map named it absolute. Source string Line, Column int}
Position is a place in a source file, line and column from 1.