add_conan_lib cmake function is defined, that allows to add a dependency using Conan with two possible system fallbacks:
1. pkg_check_modules is invoked, if `PGK_CONFIG ...` is present
2. find_package is invoked if `FIND_PACKAGE_OPTIONS` is present and `pkg_check_modules` has failed
If `ALWAYS_ALLOW_CONAN_FALLBACK` is present - `obey_system_dependencies` will be ignored for the package
Currently, the following dependencies are retrieved using Conan:
* zlib
* expat
* wxwidgets
* libmp3lame
* libid3tag
* libmad
The last three libraries are included in this commit, as they depend on zlib.
Properly pass **arch** and **os.version** to Conan