conf-files: make conf_file_new() take ConfFilesFlags rather than ChaseFlags

No functional change, preparation for later commit.

src/basic/basic-forward.h

@@ -86,6 +86,7 @@ union sockaddr_union;
 typedef enum CGroupFlags CGroupFlags;
 typedef enum CGroupMask CGroupMask;
 typedef enum ChaseFlags ChaseFlags;
+typedef enum ConfFilesFlags ConfFilesFlags;
 typedef enum ExtractFlags ExtractFlags;
 typedef enum ForkFlags ForkFlags;
 typedef enum Glyph Glyph;