build: no more recursion for lib 'subdir'

build: no more recursion for lib 'subdir'

* Makefile.am (SUBDIRS): Drop 'lib'.
(edit): New, shared among the recipes in 'lib/local.mk' and
'bin/local.mk'.
(CLEANFILES): New, will be updated later in included files.
($(srcdir)/lib/local.mk): Include it.
($(srcdir)/lib/freeze.mk): Likewise.
* lib/Makefile.am: Rename ...
* lib/local.mk: .. like this, with several adjustments.  In
particular ...
(edit): Drop this definition, subsumed by the one in the
top-level Makefile.am.
* bin/local.mk (edit): Drop definition, that is already present
in the top-level Makefile.am now.
($(srcdir)/lib/freeze.mk): Drop inclusion; that is already done
in the top-level Makefile.am now.
* doc/local.mk (CLEANFILES): Adjust: append to it, do not define
it.
* lib/freeze.mk ($(AUTOM4TE_CFG)): Adjust recipe.
* configure.ac (AC_CONFIG_FILES): Drop 'lib/Makefile'.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>