Update CHANGELOG with cplusplus fixes
in schema and JSON parser.
- Align `monster_test.fbs` Monster table more closely with Googles flatc
version after they diverged a bit. (Subtables may differ).
-- Some C++ compatiblity fixes.
+- Some C++ compatiblity fixes so `include/{support/flatcc}` headers can
+ be included into C++ without `extern "C"`.
- Fix missing null ptr check in fall-back `aligned_free`.
- Enable `posix_memalign` as a default build option on recent GNU
systems because -std=c11 blocks automatic detection. This avoids
