Synch-ed GeoModelXml with the latest updates in the Athena repository

See merge request !101

See the [merge request](atlas/athena!47262)
by Scott for more details

Rolled back two commits which affected Pow::operator()

See merge request !100

These commits are: 810d7a0f and e0e82eb7. The reason for the rollback is that
we want to understand why they lead to some changes in ATLAS G4 Sim outputs.

ExpressionEvaluator: Fix compilation warnings.

See merge request !99

GeoModelDBManager: Fix compilation warnings.

See merge request !98

GeoModelRead: Fix compilation warning.

See merge request !97

GeoModelRead: Fix placement of using directive.

See merge request !96

GeoModelKernel: Fix compilation warnings.

See merge request !94

GeoModelKernel: Fix race in RCBase::unref().

See merge request !95

Don't rely on falling through between switch cases.
Unused function parameters.

Uninitialized local variables.
Unused variable.

Unused variable.

    
Don't put a using directive in the global namespace in headers.

The decrement and test must be done atomically; otherwise we could have
a race.  E.g., suppose a RCBase object has a refcount of 2, and two threads
call unref simultaneously.  The two decrements could both happen before
either of the comparisons, resulting in a double-delete.

Order of member initialization.
Unused class data members.
Unused function parameter.

Adding 'volume filters' to GMEX

See merge request !76

Bugfix in geomodel.dtd

See merge request !91

Add material visualization for TileCal

See merge request !92

Updated geomodel.dtd with the latest changes from the Athena repository

See merge request !90

Fixes in GeoModelXml (from Scott)

See merge request !88

bug fixed in GeoModelXml/src/ReplicaRPhiProcessor.cxx

See merge request !89