swift

c060a90f - Generalize the LCA implementation in ASTScope for arbitrary macro nesting

Generalize the LCA implementation in ASTScope for arbitrary macro nesting The prior Least Common Ancestor (LCA) implementation in ASTScope, which is used to search child scopes to find a particular location, assumed that the source range it was given was contained within a single buffer and was specific to the child-scope search task. Generalize this to a more fundamental "is before" operation on source locations that respects macro expansions, simplifying the code in the process.