Rollup of 8 pull requests

.gitmodules

@@ -18,6 +18,9 @@
 [submodule "src/liblibc"]
 	path = src/liblibc
 	url = https://github.com/rust-lang/libc.git
+[submodule "src/doc/nomicon"]
+	path = src/doc/nomicon
+	url = https://github.com/rust-lang-nursery/nomicon
 [submodule "src/tools/cargo"]
 	path = src/tools/cargo
 	url = https://github.com/rust-lang/cargo

README.md

@@ -149,7 +149,7 @@ $ ./configure
 $ make && sudo make install
 ```
 
-When using the configure script, the generated config.mk` file may override the
+When using the configure script, the generated `config.mk` file may override the
 `config.toml` file. To go back to the `config.toml` file, delete the generated
 `config.mk` file.
 

src/doc/index.md

@@ -28,6 +28,7 @@ Rust provides a number of book-length sets of documentation, collectively
 nicknamed 'The Rust Bookshelf.'
 
 * [The Rust Programming Language][book] teaches you how to program in Rust.
+* [The Unstable Book][unstable-book] has documentation for unstable features.
 * [The Rustonomicon][nomicon] is your guidebook to the dark arts of unsafe Rust.
 * [The Reference][ref] is not a formal spec, but is more detailed and comprehensive than the book.
 
@@ -44,4 +45,5 @@ landed before then. That work is being tracked [here][38643].
 [err]: error-index.html
 [book]: book/index.html
 [nomicon]: nomicon/index.html
+[unstable-book]: unstable-book/index.html