Revert "GCC 4.6 compatibility: can't list-initialize array of classes."
Revert "GCC 4.6 compatibility: can't list-initialize array of classes."

It does too much harm on GCC 4.6 (all these constexpr constructors are
not constexpr now). We can disable that `-pedantic` warning for GCC 4.6
only and live with that.

This reverts commit 2d92d497d9a1b20c9ff83e386b58745955204d54.

MiUishadow/magnum,MiUishadow/magnum,DerThorsten/magnum,DerThorsten/magnum,ashimidashajia/magnum,DerThorsten/magnum,MiUishadow/magnum,MiUishadow/magnum,ashimidashajia/magnum,ashimidashajia/magnum,DerThorsten/magnum,MiUishadow/magnum,DerThorsten/magnum,ashimidashajia/magnum,MiUishadow/magnum,ashimidashajia/magnum