Merge branches 'subdirs-simplify' and 'subdir-objects-pr10697' into maint * subdirs-simplify: subdirs: unify rules for "cleaning" and "normal" recursive targets tests: add a "demo" test on C support * subdir-objects-pr10697: subdir-objects: improve "make mostlyclean" efficiency and flexibility tests: look for '.lo' rather than '.o' object when using Libtool with C++ cosmetics: few typofixes in older ChangeLogs, suggested by "codespell.py" Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>