main: Drop log builtin

We may revive this later, but commits in their current form aren't
very useful for humans to read, so it doesn't make sense to have a
tool to show a history of useless stuff.

More interesting things are diffs between commits, object statistics,
etc.

src/libotutil/ot-unix-utils.h

@@ -36,8 +36,6 @@
 
 G_BEGIN_DECLS
 
-gboolean ot_util_spawn_pager (GOutputStream  **out_stream, GError         **error);
-
 void ot_util_fatal_literal (const char *msg) G_GNUC_NORETURN;
 
 void ot_util_fatal_gerror (GError *error) G_GNUC_NORETURN;