Rename doc/manual{src -> source}

This is needed to avoid this
https://github.com/mesonbuild/meson/issues/13774 when we go back to
making our subproject directory `src`.

doc/manual/source/release-notes/rl-0.16.md

@@ -0,0 +1,25 @@
+# Release 0.16 (2010-08-17)
+
+This release has the following improvements:
+
+  - The Nix expression evaluator is now much faster in most cases:
+    typically, [3 to 8 times compared to the old
+    implementation](http://www.mail-archive.com/nix-dev@cs.uu.nl/msg04113.html).
+    It also uses less memory. It no longer depends on the ATerm library.
+
+  - Support for configurable parallelism inside builders. Build scripts
+    have always had the ability to perform multiple build actions in
+    parallel (for instance, by running `make -j
+                            2`), but this was not desirable because the number of actions to be
+    performed in parallel was not configurable. Nix now has an option
+    `--cores
+                            N` as well as a configuration setting `build-cores =
+                            N` that causes the environment variable `NIX_BUILD_CORES` to be set
+    to *N* when the builder is invoked. The builder can use this at its
+    discretion to perform a parallel build, e.g., by calling `make -j
+                            N`. In Nixpkgs, this can be enabled on a per-package basis by
+    setting the derivation attribute `enableParallelBuilding` to `true`.
+
+  - `nix-store -q` now supports XML output through the `--xml` flag.
+
+  - Several bug fixes.