Remove constexpr from filledArray().

Fixes #102 (closed), and partly #99 (closed).

This makes it compatible with C++11 and thus g++ 4.9.

filledArray() effectively wasn't constexpr anyway until C++17, where std::array becomes constexpr (for the most part, at least).

changed the description

@martin.nolte This merges directly into 2.6.

merged

mentioned in commit dec25615

mentioned in issue #102 (closed)