[libcxx] Allow use of ShTest in libc++ tests along with other changes.

Summary:
This patch allows the use of LIT's ShTest format in the libc++ test suite. ShTests have the suffix '.sh.cpp'. It also introduces a series of other changes. These changes are:

- More functionality including parsing test metadata has been moved into LIT.
- LibcxxTestFormat now supports multi-part suffixes.
- the `CXXCompiler` functionality has been used to shrink the size of LibcxxTestFormat. 
- The recursive loading of the site config has been turned into `libcxx.test.config.loadSiteConfig` so it can be used with libc++abi.
- Temporary files are now created in the build directory of libc++. This follows how it is down in ShTest.
- `not.py` was added as a utility executable that mirrors the functionality of LLVM's `not` executable. 
- The first ShTest test was added under test/libcxx/double_include.sh.cpp


Reviewers: jroelofs, danalbert

Reviewed By: danalbert

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D7073

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@226844 91177308-0d34-0410-b5e6-96231b3b80d8

test/libcxx/util.py

@@ -0,0 +1,46 @@
+from contextlib import contextmanager
+import os
+import tempfile
+
+
+def cleanFile(filename):
+    try:
+        os.remove(filename)
+    except OSError:
+        pass
+
+
+@contextmanager
+def guardedTempFilename(suffix='', prefix='', dir=None):
+    # Creates and yeilds a temporary filename within a with statement. The file
+    # is removed upon scope exit.
+    handle, name = tempfile.mkstemp(suffix=suffix, prefix=prefix, dir=dir)
+    os.close(handle)
+    yield name
+    cleanFile(name)
+
+
+@contextmanager
+def guardedFilename(name):
+    # yeilds a filename within a with statement. The file is removed upon scope
+    # exit.
+    yield name
+    cleanFile(name)
+
+
+@contextmanager
+def nullContext(value):
+    # yeilds a variable within a with statement. No action is taken upon scope
+    # exit.
+    yield value
+
+
+def makeReport(cmd, out, err, rc):
+    report = "Command: %s\n" % cmd
+    report += "Exit Code: %d\n" % rc
+    if out:
+        report += "Standard Output:\n--\n%s--\n" % out
+    if err:
+        report += "Standard Error:\n--\n%s--\n" % err
+    report += '\n'
+    return report