fix up doc submodules

diff --git a/src/doc/book b/src/doc/book
index 2bd5d42c9956369132228da6409f0e68da56c51a..2cd1b5593d26dc6a03c20f8619187ad4b2485552 160000 (submodule)
--- a/src/doc/book
+++ b/src/doc/book
@@ -1 +1 @@
-Subproject commit 2bd5d42c9956369132228da6409f0e68da56c51a
+Subproject commit 2cd1b5593d26dc6a03c20f8619187ad4b2485552

diff --git a/src/doc/nomicon b/src/doc/nomicon
index 8ca261268068d80c0969260fff15199bad87b587..960d610e7f33889a2577f5f17c26f0d5c82b30df 160000 (submodule)
--- a/src/doc/nomicon
+++ b/src/doc/nomicon
@@ -1 +1 @@
-Subproject commit 8ca261268068d80c0969260fff15199bad87b587
+Subproject commit 960d610e7f33889a2577f5f17c26f0d5c82b30df

diff --git a/src/doc/reference b/src/doc/reference
index 3ae62681ff236d5528ef7c8c28ba7c6b2ecc6731..2cb0ed9ba56360949f492f9866afe8c293f9f9da 160000 (submodule)
--- a/src/doc/reference
+++ b/src/doc/reference
@@ -1 +1 @@
-Subproject commit 3ae62681ff236d5528ef7c8c28ba7c6b2ecc6731
+Subproject commit 2cb0ed9ba56360949f492f9866afe8c293f9f9da

diff --git a/src/doc/rust-by-example b/src/doc/rust-by-example
index 8888f9428fe9a48f31de6bd2cef9b9bf80791edc..a9fb7d13eadfcc5f457962731f105b97f9a7474a 160000 (submodule)
--- a/src/doc/rust-by-example
+++ b/src/doc/rust-by-example
@@ -1 +1 @@
-Subproject commit 8888f9428fe9a48f31de6bd2cef9b9bf80791edc
+Subproject commit a9fb7d13eadfcc5f457962731f105b97f9a7474a