Rework SG::Bases to (a) allow for an arbitrary number of base classes,
and (b) support compile-time iteration over the bases.

(This is working towards speeding up the casting operations performed
by DataProxy.)

SYCL Updates, master branch (2020.08.14.)

See merge request atlas/athena!35624

Overlay transform using ComponentAccumulator

See merge request atlas/athena!35335

Class adjustments: ElementLinkVector Identifier32 SpacePoint

See merge request atlas/athena!35622

AthenaKernel+SGTools: Move safe_clid from SGTools to AthenaKernel.

See merge request atlas/athena!35649

D3PDMakerInterfaces: cmake fixes

See merge request atlas/athena!35648

AthenaCommon: python 2 fix

See merge request atlas/athena!35645

Manual sweep from 21.0 to master of !35250: Decide whether SimHit Collections should be created per simulator on a per region-basis

See merge request atlas/athena!35605

DataQualityTools+PrimaryDPDMaker+MissingETPerformance: cmake fixes

See merge request atlas/athena!35650

Merge branch 'master-ivan-CI-12012020_3' into '21.0'

See merge request atlas/athena!35606

TriggerMenuMT: python 2 fix

See merge request atlas/athena!35627

Add issMdt method to MuonIdHelperSvc

See merge request atlas/athena!35619

Data overlay: cleanup zero bias selection scripts

See merge request atlas/athena!35610

add Gaudi::Property, SG::ReadHandleKeyArray for AnalysisBase

See merge request atlas/athena!35596

TrigConf2COOLOnline: Delete obsolete package

See merge request atlas/athena!28410

copyRootTree.cxx: Add missing include statement (LCG98 preparation)

See merge request atlas/athena!35613

GsfMeasurementUpdator:Remove un-needed allocations

See merge request atlas/athena!35593

Move JetTagCalibCondAlg to AthCondSeq

See merge request !35620

GSF tidy up a bit the caches

See merge request atlas/athena!35594

Remove documentation particles from truth record

See merge request atlas/athena!35640

MuonPrepData: noexcept_moveable for vector optimization

See merge request atlas/athena!35580

Library dependency fixes.

Library dependency fixes.

Library dependency fixes.

Define an interface library for exported headers.

    
Pickle files saved in the release should be python 2 compatible
as long as we're supporting a python 2 build.

Move the safe_clid function from SGTools to AthenaKernel.
(It currently has no clients.)

    
Move the safe_clid function from SGTools to AthenaKernel.
(It currently has no clients.)

update tests for changes to TagInfoMgr output

See merge request atlas/athena!35464

MuonCombinedBaseTools: Fix clang warning.

See merge request atlas/athena!35598

TrkVertexFitterUtils: Fix clang warning.

See merge request atlas/athena!35572

TrigConfigSvc: Fix clang wanrnings.

See merge request atlas/athena!35597

TrigTauHypo: cmake fix

See merge request atlas/athena!35599

TrigInDetAccelerationService: Fix warning.

See merge request atlas/athena!35601

SGTools: Add benchmarking code for DataProxy casting.

See merge request atlas/athena!35625