StoreGate: Remove use of obsolete CxxUtils headers.

Remove use of headers from CxxUtils that are no longer needed now that we're building with c++17.

This merge request affects 1 package:

• Control/StoreGate

Adding @ssnyder ,@rbianchi as watchers

added Core master review-pending-level-1 labels

CI Result SUCCESS

	Athena	AthSimulation
externals
cmake
make
required tests
optional tests

Full details available at NICOS MR-25105-2019-07-25-03-27
Athena: number of compilation errors 0, warnings 1
AthSimulation: number of compilation errors 0, warnings 0
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 1439]

added review-approved label and removed review-pending-level-1 label

mentioned in commit c84f1c0f

merged

added sweep:ignore label