maint: reduce use of recursion in automake build system Recursive make-based build systems tend to be slower, more fragile and less faithful than "flat" ones. See Peter Miller's article "Recursive Make Considered Harmful" for more a more in-depth discussion: <http://miller.emu.id.au/pmiller/books/rmch/> While in the case of automake this isn't a big problem (given the small size of its build systems), it still creates occasional glitches and annoyances. So, with this change, we start making less use of make recursion in the Automake's own build system (future changes will reduce it even more). * lib/am/Makefile.am, lib/Automake/Makefile.am: Removed, their content merged ... * lib/Makefile.am: ... here, with required adjustments. * configure.ac (AC_CONFIG_FILES): Update. Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>