Bless test.

Bless test, remove submodule, and fix book entry.

bless test again? maybe it'll work this time...

Author: repnop

Diff for: src/doc/rustdoc/src/unstable-features.md

@@ -420,4 +420,12 @@ renamed with `--resource-suffix` will load from the given path.
 
 ### `--persist-doctests`: persist doctest executables after running
 
-This feature allows the persistence of the doctest executables to the specified path.
+Using this flag looks like this:
+
+```bash
+$ rustdoc src/lib.rs --test -Z unstable-options --persist-doctests target/rustdoctest
+```
+
+This flag allows you to keep doctest executables around after they're compiled or run.
+Usually, rustdoc will immediately discard a compiled doctest after it's been tested, but
+with this option, you can keep those binaries around for farther testing.

Diff for: src/test/rustdoc-ui/failed-doctest-output.stdout

@@ -12,7 +12,7 @@ error[E0425]: cannot find value `no` in this scope
 3 | no
   | ^^ not found in this scope
 
-thread '$DIR/failed-doctest-output.rs - OtherStruct (line 27)' panicked at 'couldn't compile the test', src/librustdoc/test.rs:361:13
+thread '$DIR/failed-doctest-output.rs - OtherStruct (line 17)' panicked at 'couldn't compile the test', src/librustdoc/test.rs:354:13
 note: Run with `RUST_BACKTRACE=1` environment variable to display a backtrace.
 
 ---- $DIR/failed-doctest-output.rs - SomeStruct (line 11) stdout ----
@@ -21,7 +21,7 @@ thread '$DIR/failed-doctest-output.rs - SomeStruct (line 11)' panicked at 'test
 thread 'main' panicked at 'oh no', $DIR/failed-doctest-output.rs:3:1
 note: Run with `RUST_BACKTRACE=1` environment variable to display a backtrace.
 
-', src/librustdoc/test.rs:396:17
+', src/librustdoc/test.rs:389:17
 
 
 failures: