Speed up integration tests (move building expectations)

Speed up running 'cargo test':
-Before: 2'17s
-After: 30s

For every 'cargo test' run, the bindgen output where built.
We already test that the bindgen output match expectations/*.rs,
so there is no need to check it build unless the expectation is updated.

Move tests/expectations/*.rs to tests/expectations/tests/*.rs and make
tests/expectations a new dev-dependency package. This allow running:
 - cargo test -p tests_expectations

In addition to the speed up, we also get a clean output for the build
and test run. In particular, a number of warnings are generated that should
probably be silenced, and eventually enforced modifying travis to build:
 - RUSTFLAGS='-D warnings' cargo test -p tests_expectations

The benefit of having it as a new package is that it avoid polluting
the 'cargo test' output that should focus on bindgen.

Author: jeanphilippeD

.travis.yml

@@ -33,6 +33,7 @@ script:
   - git add -A
   - git diff @
   - git diff-index --quiet HEAD
+  - cargo test -p tests_expectations
   - cargo build --features "$BINDGEN_FEATURES _docs"
 
 notifications:

Cargo.toml

@@ -54,5 +54,8 @@ _docs = []
 name = "bindgen"
 path = "src/lib.rs"
 
+[dev-dependencies.tests_expectations]
+path = "tests/expectations"
+
 [[test]]
 name = "tests"

tests/expectations/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "tests_expectations"
+description = "bindgen results when ran on ../headers/*"
+version = "0.1.0"
+authors = [
+  "Jyun-Yan You <[email protected]>",
+  "Emilio Cobos Álvarez <[email protected]>",
+  "The Servo project developers",
+]
+
+[dependencies]