Remove redundant middle_end/dune file and commented-out section from backend/dune

Author: mshinwell

backend/dune

@@ -42,36 +42,3 @@
        (progn
          (bash "echo \\# 1 \\\"`cat contains-input-name`\\\"")
          (bash "%{dep:../ocaml/tools/cvt_emit.exe} < `cat contains-input-name`"))))))
-
-; Moved to toplevel dune file -- see comment there.
-;
-; Since there are files with the same name in more than one directory,
-; e.g. proc.ml, then we can't use "include_subdirs unqualified".  Instead we
-; extract the files manually from subdirectories.
-;(copy_files debug/*.ml{,i})
-;
-;(library
-;  (name ocamloptcomp)
-;  (public_name flambda_backend.ocamloptcomp)
-;  (wrapped false) ; also for compatibility with existing code
-;  (modes byte native)
-;  ; We should change the code so this "-open" can be removed.
-;  ; Likewise fix occurrences of warning 9.
-;  (flags (:standard -principal -nostdlib -w -9))
-;  (modules_without_implementation x86_ast)
-;  ; The driver should be in here too, if we want to match upstream.
-;  (modules
-;    ;; asmcomp/
-;    afl_instrument arch asmgen asmlibrarian asmlink asmpackager
-;    branch_relaxation branch_relaxation_intf cmm_helpers cmm cmmgen
-;    cmmgen_state coloring comballoc CSE CSEgen deadcode emit
-;    emitaux interf interval linear linearize linscan liveness mach printcmm
-;    printlinear printmach proc reg reload reloadgen schedgen scheduling
-;    selectgen selection spacetime_profiling spill split strmatch x86_ast
-;    x86_dsl x86_gas x86_masm x86_proc
-;
-;    ;; asmcomp/debug/
-;    reg_availability_set compute_ranges_intf available_regs reg_with_debug_info
-;    compute_ranges)
-;  (libraries ocaml.ocamlcommon flambda_backend.ocamlmiddleend ocaml.stdlib))
-;