Variety of improvements

- Rename sources to distfiles for clarity.
- Per sys(a/c) distfiles to reduce rootfs.py processing and reduce RAM
  usage in sysa.
- Canonicalise early kaem mes/tcc files to kaem script conventions.
- Cleanup unused setup in python.

sysa/patch-2.5.9/patch-2.5.9.kaem

@@ -10,7 +10,7 @@ mkdir build src
 cd build
 
 # Extract
-cp ${sources}/${pkg}.tar.gz ../src/
+cp ${distfiles}/${pkg}.tar.gz ../src/
 gunzip -f ../src/${pkg}.tar.gz
 tar xf ../src/${pkg}.tar
 cd ${pkg}