Merge 5.2.0minus 3 (#119) * Update import scripts * Import ocaml sources for ocaml-flambda/flambda-backend@e1efceb89a5 * Automatic merges * Commit conflicts * Remove files that were deleted in flambda * Apply old diff to language_extension * Resolve conflicts * Resolve errors outside of merlin-specific code * Resolve more issues * Fix more issues * Update magic number script * Bump magic numbers * Promote tests * Add comments about subdirectory * Use Ast_helper.Sg.mk