Unfortunately ABI was broken when symbols files were removed
in favour of new visibility control of exported functions.
Visibility control with -fvisibility works fine, but symbol
scripts had another feature - versioned symbols. And we lost it.
Since we can not make our symbols to be versioned with the new
approach, it's decided to return everything back.
* CMake: Restore symbol files generation
* CMake: Python is required to build shared libraries
* Autotools: Restore symbol files generation
Closes: https://github.com/erikd/libsndfile/issues/268
This allows parallel builds of different LibSndFile configurations
- results of configure_file and AutoGen are saved in CMAKE_BINARY_DIR
- the directory ${CMAKE_BINARY_DIR}/src is make a public include directory
- remove generated files in source tree prior to generation + fix install
Related: https://github.com/erikd/libsndfile/issues/71