docs: fix build error
Merge pull request #24 from evojimmy/changes

docs: fix build error
marsystems: AudioSink: fix and refactor
marsystems: MidiInput: keep compilers happy in non-C++11 mode
marsystems: SVFilter: do not use C++11 features

Sorry, our current policy is to avoid C++11 if not necessary.

You can use C++11 only in code that is compiled conditionally when the
'WITH_CPP11' CMake option is enabled.