v5.3.2

A build system release: unordered_dense can now be used as a Meson subproject. The header is unchanged apart from the version, same hash values and same iteration order as 5.3.1.

• meson.build declares unordered_dense_dep and registers it with meson.override_dependency(), so a project that has unordered_dense in its subprojects/ gets it with dependency('unordered_dense'), version constraints included. When used as a subproject, the tests are not built, so doctest, fmt and boost are no longer needed (#382, thanks @ibc!).

The inline namespace is v5_3_2.