make the hooks usable by the whole catalogue

- hooks load the _stack files of every directory between the stack path root
  and the stack, outermost first: make included both $(dir)/*.mk and
  $(dir)/*/*.mk, so a stack in a subdirectory saw its parent's settings
- a group may be declared in <group>/<group>.env, where the stack lives
- MYOS_STACK_DIR lets a hook read a file it ships next to itself
- myos_filter no longer confuses a literal * in a make pattern with a wildcard,
  and the list helpers no longer let the shell expand a * into filenames
- MACHINE, SYSTEM, HOST and DOMAINNAME join the framework variables a hook sees
- the make shim gains $(call myos-var,NAME), so a .mk target can read a
  setting that now lives in a hook, and it picks up the .mk of every stack
  directory rather than only the project's

spec/unit/hooks_spec.sh

@@ -5,6 +5,7 @@ Include lib/var.sh
 Include lib/tags.sh
 Include lib/naming.sh
 Include lib/config.sh
+Include lib/stack.sh
 Include lib/hooks.sh
 
 # A stack ships its computed settings as a shell hook, so the catalogue works
@@ -14,6 +15,7 @@ Describe 'lib/hooks.sh'
     MYOS_TMP=$(mktemp -d "${TMPDIR:-/tmp}/myos-hook.XXXXXX")
     MYOS_TMP=$(cd "$MYOS_TMP" && pwd -P)
     ENV=local; DOMAIN=example.org; USER=tester; HOSTNAME=testhost
+    MYOS_PATH=$MYOS_TMP
     APP_HOST=demo.example.org; APP_URI=demo.example.org/
   }
   cleanup() { rm -rf "$MYOS_TMP"; }