traits: rename to std:: naming convention

sed -e 's/\<IsSimdArray\>/is_simd_array/g' \
~Vc-staging (operator_subscript+stash) 11:37
-e 's/\<IsSubscriptOperation\>/is_subscript_operation/g' \
-e 's/\<IsLoadStoreFlag\>/is_load_store_flag/g' \
-e 's/\<VectorSize\>/simd_vector_size/g' \
-e 's/\<IsCastArguments\>/is_cast_arguments/g' \
-i **/*.{h,tcc,cpp}

(I had to revert a few VectorSize occurrences)

refs #604

Signed-off-by: Matthias Kretz <kretz@kde.org>
traits: remove duplicated trait, making simd_vector_size work for simdarray

Signed-off-by: Matthias Kretz <kretz@kde.org>