CxxUtils: vec.h move recurring macro to features.h to avoid repeating code

CxxUtils vec.h move recurring macro on if ternary is supported for vector types to features.h to avoid repeating it.

Also we have HAVE_TARGET_CLONES for that particular feature of gcc (both clang and gcc have target).

changed the description

This merge request affects 1 package:

• Control/CxxUtils

Adding @ssnyder ,@rbianchi as watchers

added Core master review-pending-level-1 labels

CI Result SUCCESS (hash af918fc9)

	Athena	AthSimulation	AthGeneration	AnalysisBase
externals
cmake
make
required tests
optional tests

Full details available on this CI monitor view
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
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 19737]

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

merged

mentioned in commit b664ad6a

added sweep:ignore label