I see that some new versions of packages are installed without
the old versions being removed, although they are marked as
automatically installed, e.g. Linux kernel, clang, llvm, and
some others. For example
# aptitude search "~i clang"
i clang - C, C++ and Objective-C compiler (LLVM based)
i A clang-3.5 - C, C++ and Objective-C compiler (LLVM based)
i A libclang-common-3.5-dev - clang library - Common development package
i A libclang1-3.5 - C interface to the clang library
and aptitude full-upgrade will install clang-3.8 but not
M. Thuermann did explicitly say clang-3.5, not clang.