Rework vs.xml: hardening, query builder, C API, xmake (v0.3.1)

- Harden binary loading and fix ownership.
- Parser and serializer correctness; pretty-printing.
- Replace the query generator with an explicit builder.
- Add C bindings (vs-xml/c.h).
- Switch to xmake; drop Meson/CMake; move headers to vs-xml/.
- Portability fixes for clang: explicit class NTTPs, drop glibc endian.h.
- Release prep for v0.3.1.

Preparing release

Release v0.2.11

Preparing release (#20)

Early release of v0.2.7 because things broke in the earlier one

Fix

Release

Create FUNDING.yml

Fixed release

Planning benchmarks, extending docs