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 *
This type represents templatized names, and replaces our previous use
of 'TemplatizedType' and 'TemplatizedFunctionCall'.
Also, we now parse function calls as secondary expressions.
After we moved to storing the text of each token in the token itself,
we no longer have to store the source of the program in the Parser.
This makes more sense because the parser should deal with tokens, not
with raw source code.
We now also look at the available declarations from included header
files when autocompleting names.
Additionally, you can now request autocomplete on an empty token, which
brings up all available names, starting from the inner-most scope.
This parser will be used by the C++ langauge server to provide better
auto-complete (& maybe also other things in the future).
It is designed to be error tolerant, and keeps track of the position
spans of the AST nodes, which should be useful later for incremental
parsing.
