Add the first Conan-based dependecies

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

cmake-proxies/libid3tag/CMakeLists.txt

@@ -27,7 +27,6 @@ list( APPEND SOURCES
 list( APPEND INCLUDES
    PRIVATE
       ${_PRVDIR}
-      $<$<PLATFORM_ID:Windows>:$ENV{WXWIN}/src/zlib>
    PUBLIC
       ${TARGET_ROOT}
 )
@@ -39,7 +38,7 @@ list( APPEND OPTIONS
 
 list( APPEND LIBRARIES
    PRIVATE
-     wxWidgets
+     
 )
 
 configure_file( config.h.in private/config.h )