Add CMake and tests

- Port tests to GitLab
- Add GitLab CI test matrix
- Remove gtest submodule

CHANGES.md

@@ -0,0 +1,17 @@
+# Changes
+
+## 0.9.0
+
+- Forked to the DkML repository on GitLab.
+- Use binary mode when reading schemas on Windows
+- Use SSIZE_T from `BaseTsd.h` to allow MSVC to compile with 32-bits
+- Put alignment on segment fields, not just the structure.
+- Avoids left shifts of signed integers, which is undefined C behavior. Passes
+  ASAN (not a false positive)
+- Wrap macro parameters in the `capnp_use(x)` macro. Passes clang-tidy (not
+  a false positive)
+
+
+## 0.3 (632f0d73a1f4a03026b5e4727386b9fe3ec6e00e)
+
+- Fork of `c-capnproto-0.3` plus several untagged commits from https://github.com/opensourcerouting/c-capnproto on Apr 23, 2023. Specifically: https://github.com/opensourcerouting/c-capnproto/commit/632f0d73a1f4a03026b5e4727386b9fe3ec6e00e