Contains all of the IDL files except those in [[udkapi]]

i.e. the interfaces that are specific to the LibreOffice application.
An artificial (?) separation.

The reference offapi/type_reference/offapi.idl and
udkapi/type_reference/udkapi.idl (formerly combined into a single
offapi/type_reference/types.rdb) are used to detect inadvertent incompatible
changes.  They are plain-text .idl files (not stricly lexicographically sorted,
though, so they satisfy the .idl file requirements for no forward dependencies),
so in cases where we deliberately /do/ become incompatible they can be modified
manually.

Old such cases of deliberately becoming incompatible are listed in
offapi/type_reference/typelibrary_history.txt, newer such cases are recorded in
the git logs of (now superseded) offapi/type_reference/types.rdb,
offapi/type_reference/offapi.rdb, and udkapi/type_reference/udkapi.rdb, new such
cases are recorded in the git logs of offapi/type_reference/offapi.idl and
udkapi/type_reference/udkapi.idl.