Implement parsing, AST, (de-)serialization, and placeholder global

metadata for linking against the libraries/frameworks for imported
modules.

The module map language is extended with a new "link" directive that
specifies what library or framework to link against when a module is
imported, e.g.,

  link "clangAST"

or

  link framework "MyFramework"

Importing the corresponding module (or any of its submodules) will
eventually link against the named library/framework.

For now, I've added some placeholder global metadata that encodes the
imported libraries/frameworks, so that we can test that this
information gets through to the IR. The format of the data is still
under discussion.

llvm-svn: 172437

clang/lib/Basic/Module.cpp

@@ -257,6 +257,16 @@ void Module::print(raw_ostream &OS, unsigned Indent) const {
     OS << "\n";
   }
 
+  for (unsigned I = 0, N = LinkLibraries.size(); I != N; ++I) {
+    OS.indent(Indent + 2);
+    OS << "link ";
+    if (LinkLibraries[I].IsFramework)
+      OS << "framework ";
+    OS << "\"";
+    OS.write_escaped(LinkLibraries[I].Library);
+    OS << "\"";
+  }
+
   if (InferSubmodules) {
     OS.indent(Indent + 2);
     if (InferExplicitSubmodules)