After this commit, Parser::index_of_node_at will prefer to return nodes
with greater indices.
Since the parsing logic ensures that child nodes come after parent
nodes, this change makes this function return child nodes when possible.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
