Add cffi v1.7 test

This new version is causing some issues for us

test/extra/cffi_1.7_test.py

+# Note: the expected counts here are set to match the CI, and I can't reproduce them locally
+import os, sys, subprocess, shutil
+sys.path.append(os.path.dirname(__file__) + "/../lib")
+
+from test_helper import create_virtenv, run_test
+
+ENV_NAME = "cffi17_test_env_" + os.path.basename(sys.executable)
+SRC_DIR = os.path.abspath(os.path.join(ENV_NAME, "src"))
+PYTHON_EXE = os.path.abspath(os.path.join(ENV_NAME, "bin", "python"))
+PYTEST_EXE = os.path.abspath(os.path.join(ENV_NAME, "bin", "py.test"))
+
+def install_and_test_cffi():
+    shutil.rmtree(SRC_DIR, ignore_errors=True)
+    os.makedirs(SRC_DIR)
+
+    url = "https://pypi.python.org/packages/83/3c/00b553fd05ae32f27b3637f705c413c4ce71290aa9b4c4764df694e906d9/cffi-1.7.0.tar.gz#md5=34122a545060cee58bab88feab57006d"
+    subprocess.check_call(["wget", url], cwd=SRC_DIR)
+    subprocess.check_call(["tar", "-zxf", "cffi-1.7.0.tar.gz"], cwd=SRC_DIR)
+    CFFI_DIR = os.path.abspath(os.path.join(SRC_DIR, "cffi-1.7.0"))
+
+    subprocess.check_call([PYTHON_EXE, "setup.py", "install"], cwd=CFFI_DIR)
+
+    # looks like clang 3.5 causes more errors like: 214 != -42 doing casts
+    if os.environ.has_key("CC") and "clang" in os.environ["CC"]:
+        expected = [{ "failed": 20, "passed": 1659, "skipped": 73, "xfailed": 4}]
+    else:
+        expected = [{ "failed": 11, "passed": 1668, "skipped": 73, "xfailed": 4}]
+    run_test([PYTEST_EXE], cwd=CFFI_DIR, expected=expected)
+
+create_virtenv(ENV_NAME, ["pytest==2.8.7", "py==1.4.31", "pycparser==2.14"], force_create = True)
+install_and_test_cffi()

test/extra/cffi_test.py

-# Note: the expected counts here are set to match the CI, and I can't re[rpduce them locally
+# Note: the expected counts here are set to match the CI, and I can't reproduce them locally
 import os, sys, subprocess, shutil
 sys.path.append(os.path.dirname(__file__) + "/../lib")