replace two shuffle calls by Mem::permute helper to avoid bogus warning with clang
replace two shuffle calls by Mem::permute helper to avoid bogus warning with clang

chr-engwer/Vc,chr-engwer/Vc,chr-engwer/Vc,VcDevel/Vc,VcDevel/Vc,VcDevel/Vc,VcDevel/Vc