CxxUtils: Add ConcurrentRangeMap::clear().

Mostly for testing --- should not normally be used.

This merge request affects 1 package:

• Control/CxxUtils

This merge request affects 4 files:

• Control/CxxUtils/CxxUtils/ConcurrentRangeMap.h
• Control/CxxUtils/CxxUtils/ConcurrentRangeMap.icc
• Control/CxxUtils/share/ConcurrentRangeMap_test.ref
• Control/CxxUtils/test/ConcurrentRangeMap_test.cxx

Adding @ssnyder ,@rbianchi as watchers

added Core master review-pending-level-1 labels

CI Result SUCCESS (hash 52e7f5f8)

	Athena	AthSimulation	AthGeneration	AnalysisBase	AthAnalysis	DetCommon
externals
cmake
make
tests

Full details available on this CI monitor view. Check the JIRA CI status board for known problems
Athena: number of compilation errors 0, warnings 0
AthSimulation: number of compilation errors 0, warnings 0
AthGeneration: number of compilation errors 0, warnings 0
AnalysisBase: number of compilation errors 0, warnings 0
AthAnalysis: number of compilation errors 0, warnings 0
DetCommon: number of compilation errors 0, warnings 0
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 62971]

added review-approved label

removed review-pending-level-1 label

merged

mentioned in commit e7d0dcdd

added sweep:ignore label