new: port the meson, cmake and autotools template bodies to manifests

data/templates/autotools/manifest.yml

@@ -1,8 +1,13 @@
 ## The `autotools` template: a C project with a configure.ac built through
 ## debhelper's auto-detection (dh runs autoreconf itself when it finds
-## configure.ac, debhelper >= 10 — no override needed). The logic half —
-## the AC_INIT probe, the skeleton bodies and the gettext detection
-## (appended to Build-Depends) — lives in src/new/templates/autotools.rs.
+## configure.ac, debhelper >= 10 — no override needed). The skeleton bodies
+## below are static data (the first source build runs `autoreconf`,
+## integrated in the dh sequence, so no generated configure script is
+## committed); the logic half — the AC_INIT probe and the GNU-gettext
+## detection (appended to Build-Depends) — lives in
+## src/new/templates/autotools.rs. hello.c.tpl duplicates the shared C
+## skeleton of the other C/C++ template directories (see
+## meson/manifest.yml for why).
 ##
 ## Schema: see src/new/templates/mod.rs.
 
@@ -16,4 +21,10 @@ build_depends:
   - libtool
 architecture: any
 rules_dh_line: "dh $@"
-files: []
+files:
+  - path: configure.ac
+    template: configure.ac.tpl
+  - path: Makefile.am
+    template: Makefile.am.tpl
+  - path: hello.c
+    template: hello.c.tpl