patch 8.2.2239: Vim9: concatenating lines with backslash is inconvenient

Problem:    Vim9: concatenating lines with backslash is inconvenient.
Solution:   Support concatenating lines starting with '|', useful for
            :autocmd, :command, etc. (closes #6702)
diff --git a/src/proto/vim9compile.pro b/src/proto/vim9compile.pro
index 3f8ae13..52ccb06 100644
--- a/src/proto/vim9compile.pro
+++ b/src/proto/vim9compile.pro
@@ -5,7 +5,6 @@
 int get_script_item_idx(int sid, char_u *name, int check_writable, cctx_T *cctx);
 imported_T *find_imported(char_u *name, size_t len, cctx_T *cctx);
 imported_T *find_imported_in_script(char_u *name, size_t len, int sid);
-int vim9_comment_start(char_u *p);
 char_u *peek_next_line_from_context(cctx_T *cctx);
 char_u *next_line_from_context(cctx_T *cctx, int skip_comment);
 char_u *to_name_end(char_u *arg, int use_namespace);
@@ -15,7 +14,7 @@
 int assignment_len(char_u *p, int *heredoc);
 void vim9_declare_error(char_u *name);
 int check_vim9_unlet(char_u *name);
-int compile_def_function(ufunc_T *ufunc, int set_return_type, cctx_T *outer_cctx);
+int compile_def_function(ufunc_T *ufunc, int check_return_type, cctx_T *outer_cctx);
 void set_function_type(ufunc_T *ufunc);
 void delete_instr(isn_T *isn);
 void unlink_def_function(ufunc_T *ufunc);
diff --git a/src/proto/vim9script.pro b/src/proto/vim9script.pro
index c386602..0eced60 100644
--- a/src/proto/vim9script.pro
+++ b/src/proto/vim9script.pro
@@ -2,6 +2,7 @@
 int in_vim9script(void);
 void ex_vim9script(exarg_T *eap);
 int not_in_vim9(exarg_T *eap);
+int vim9_comment_start(char_u *p);
 void ex_export(exarg_T *eap);
 void free_imports_and_script_vars(int sid);
 void mark_imports_for_reload(int sid);