Issues in gausscheby2

[susilehtola]

The weight used in gausscheby2 are incorrect.

IntegratorXX/include/integratorxx/quadratures/gausscheby2.hpp

Line 50 in 3c7e9ab

weight_container weights( npts, pi_ov_npts_p_1 );

There are two problems here. Compared to the equations given on Wikipedia

• the sine squared term is missing, and
• the transformation to unit weight - which is present in gausscheby1 - is also missing.

[susilehtola]

These issues are resolved in the proposed pull request.