- Add a keymap test with decimal and hexadecimal keysyms.
- Reorganize code in `test/keysym.c` by parsing type: name, Unicode and
hexadecimal.
- Add more tests for edge cases. In particular:
- test decimal format (currently not supported);
- test the Unicode and hexadecimal ranges more thoroughly;
- test with wrong case without the XKB_KEYSYM_CASE_INSENSITIVE flag;
- test surrounding spaces.
- Document the tests.