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

lib/stack.sh

@@ -171,9 +171,12 @@ myos_group_value() {
   _IFS=$IFS; IFS=:
   for _d in $(myos_path); do
     IFS=$_IFS
-    [ -f "$_d/$1.env" ] && { _v=$(sed -n "s/^$1=//p" "$_d/$1.env" | tail -1 | tr -d '"'); }
-    [ -z "$_v" ] && [ -f "$_d/$1.mk" ] && { _v=$(myos_mk_group "$_d/$1.mk" "$1"); }
-    [ -z "$_v" ] && [ -f "$_d/$1/$1.mk" ] && { _v=$(myos_mk_group "$_d/$1/$1.mk" "$1"); }
+    for _f in "$_d/$1.env" "$_d/$1/$1.env" "$_d/$1/_stack.env"; do
+      [ -z "$_v" ] && [ -f "$_f" ] && _v=$(sed -n "s/^$1=//p" "$_f" | tail -1 | tr -d '"')
+    done
+    for _f in "$_d/$1.mk" "$_d/$1/$1.mk"; do
+      [ -z "$_v" ] && [ -f "$_f" ] && _v=$(myos_mk_group "$_f" "$1")
+    done
     [ -n "$_v" ] && { printf '%s' "$_v"; return 0; }
     IFS=:
   done