Add documentation generation test

Author: MaxDesiatov

test/Documentation/docc.swift

@@ -0,0 +1,10 @@
+// REQUIRES: OS=macosx
+
+// RUN: %empty-directory(%t)
+// RUN: mv $(dirname %utils)/docs $(dirname %utils)/docs.docc
+// RUN: xcrun docc convert --output-path %t $(dirname %utils)/docs.docc
+// RUN: mv $(dirname %utils)/docs.docc $(dirname %utils)/docs
+
+// the generated bundle should be at least as big as all of the markdown files in the source directory
+// RUN: test $(du -c %t | tail -1 | awk '{ print $1 }') -gt $(du -c $(dirname %utils)/docs/*.md | tail -1 | awk '{ print $1 }') && echo success
+// CHECK: success