protobuf21-21.12-160000.2.2

- rename to protobuf21 and provide cpp bindings only for now
  as protobuf 22 is disruptive

- Mention the rpmlintrc file in the spec.

- Make possible to build on older systems, like SLE12 that miss
  some of the used macros.

- Enable LTO (boo#1133277).

- update to v21.12:
  * Python
  * Fix broken enum ranges (#11171)
  * Stop requiring extension fields to have a sythetic oneof (#11091)
  * Python runtime 4.21.10 not works generated code can not load valid
    proto.

- update to 21.11:
  * Python
  * Add license file to pypi wheels (#10936)
  * Fix round-trip bug (#10158)

- update to 21.10:
  * Java
  * Use bit-field int values in buildPartial to skip work on unset groups of
    fields. (#10960)
  * Mark nested builder as clean after clear is called (#10984)

- update to 21.9:
  * Ruby
  * Replace libc strdup usage with internal impl to restore musl compat (#10818)
  * Auto capitalize enums name in Ruby (#10454) (#10763)
  * Other
  * Fix for grpc.tools #17995 & protobuf #7474 (handle UTF-8 paths in argumentfile) (#10721)
  * C++
  * 21.x No longer define no_threadlocal on OpenBSD (#10743)
  * Java
  * Mark default instance as immutable first to avoid race during static initialization of default instances (#10771)
  * Refactoring java full runtime to reuse sub-message builders and prepare to
    migrate parsing logic from parse constructor to builder.
  * Move proto wireformat parsing functionality from the private "parsing
    constructor" to the Builder class.
  * Change the Lite runtime to prefer merging from the wireformat into mutable
    messages rather than building up a new immutable object before merging. This
    way results in fewer allocations and copy operations.
  * Make message-type extensions merge from wire-format instead of building up
    instances and merging afterwards. This has much better performance.
  * Fix TextFormat parser to build up recurring (but supposedly not repeated)
    sub-messages directly from text rather than building a new sub-message and
    merging the fully formed message into the existing field.

- update to 21.6:
  C++:
  * Reduce memory consumption of MessageSet parsing

- update to 21.5:
  PHP
  * Added getContainingOneof and getRealContainingOneof to descriptor.
  * fix PHP readonly legacy files for nested messages
  Python
  * Fixed comparison of maps in Python.