Add a reference kind for the following write reference:
Foo'Access
Foo'Unrestricted_Access
Foo'Address
Foo'Unchecked_Access
It allows to filter them from more common write reference like
"assignment" ("Foo :=").
Adapt tests. (using sed)
Add a test.
Add an operation Find_All_Base_Declarations in the Context to wrap
around the Libadalang primitive. Use this in response to 'definition'
requests.
Add new AlsReferenceKind enumerations to allow labeling the returned
results. Modify the tests to account for this new enumeration.
