aedi: add tier 3 for libraries

it will contain obsolete targets with the following properties:
* libraries that are no longer used by main targets
* these targets are no longer updated
* no binaries inside the repository

aedi/target/__init__.py

@@ -18,6 +18,7 @@
 
 from .library_tier1 import *
 from .library_tier2 import *
+from .library_tier3 import *
 from .main import *
 from .special import *
 from .tools import *

aedi/target/library_tier3.py

@@ -0,0 +1,17 @@
+#
+#    Helper module to build macOS version of various source ports
+#    Copyright (C) 2020-2022 Alexey Lysiuk
+#
+#    This program is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU General Public License as published by
+#    the Free Software Foundation, either version 3 of the License, or
+#    (at your option) any later version.
+#
+#    This program is distributed in the hope that it will be useful,
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#    GNU General Public License for more details.
+#
+#    You should have received a copy of the GNU General Public License
+#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#