- add Hilbert_{\R}{f}(z), the Hilbert transform on the real line for
periodic functions on [a,b). This is equivalent to the cotangent
version. However, it breaks with the convention of the package that the
domain of integration of the singular integral operator should be
defined by the domainspace. Perhaps this case could be an exception?

fix a typo in periodicline

time evolution uses BDF2

basis is LaurentDirichlet(PeriodicLine())

# Conflicts:
#	test/runtests.jl

# Conflicts:
#	src/stieltjesmoment.jl