[vectorIntrinsics] RFR: Cleanup code for SVML support

[Vladimir Ivanov]

Thanks, Paul.

> c2_globals.hpp:
> 
>   727   experimental(bool, UseVectorStubs, false,                                 \
>   728           "Use SVML stubs for vector trigonometric functions")              \
>   729
> 
> Trivially it's more that just trigonometric functions, currently it is transcendental functions.  Also should we drop the SVML if say stubs are included for ARM in the future?
> 
> “Use stubs for vector transcendental operations”
> 
> ?

Good point. Your variant looks good.

Best regards,
Vladimir Ivanov