ProjectExplorer: Shorten space needed to store a FileType

Use class enum to shorten the FileType to quint16. This frees up a couple
of bytes per FileNode and we can have many of those.

Change-Id: I3a9ae25059690fefa15305a4268269647d6dc1c9
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/autotoolsprojectmanager/autotoolsproject.cpp

@@ -222,8 +222,9 @@ void AutotoolsProject::makefileParsingFinished()
     QList<FileNode *> fileNodes = Utils::transform(files, [dir](const QString &f) {
         const Utils::FileName path = Utils::FileName::fromString(dir.absoluteFilePath(f));
         return new FileNode(path,
-                            (f == QLatin1String("Makefile.am") || f == QLatin1String("configure.ac"))
-                            ? ProjectFileType : ResourceType, false);
+                            (f == QLatin1String("Makefile.am") ||
+                             f == QLatin1String("configure.ac")) ? FileType::Project : FileType::Resource,
+                            false);
     });
     rootProjectNode()->buildTree(fileNodes);