Special-case the standard library to always live relative to the compiler.

Import "swift" will now only find "swift.swiftmodule", and only in the
runtime import path.

<rdar://problem/15898866>

Swift SVN r12932

lib/Serialization/Deserialization.cpp

@@ -1158,7 +1158,8 @@ Module *ModuleFile::getModule(Identifier name) {
       auto importer = getContext().getClangModuleLoader();
       assert(importer && "no way to import shadowed module");
       ShadowedModule = importer->loadModule(SourceLoc(),
-                                            std::make_pair(name, SourceLoc()));
+                                            std::make_pair(name, SourceLoc()),
+                                            false);
     }
 
     return ShadowedModule;