patch 8.2.4603: sourcing buffer lines is too complicated

Problem:    Sourcing buffer lines is too complicated.
Solution:   Simplify the code. Make it possible to source Vim9 script lines.
            (Yegappan Lakshmanan, closes #9974)
diff --git a/src/proto/scriptfile.pro b/src/proto/scriptfile.pro
index d0ebdda..510fb56 100644
--- a/src/proto/scriptfile.pro
+++ b/src/proto/scriptfile.pro
@@ -32,6 +32,7 @@
 void free_autoload_scriptnames(void);
 linenr_T get_sourced_lnum(char_u *(*fgetline)(int, void *, int, getline_opt_T), void *cookie);
 char_u *getsourceline(int c, void *cookie, int indent, getline_opt_T options);
+int sourcing_a_script(exarg_T *eap);
 void ex_scriptencoding(exarg_T *eap);
 void ex_scriptversion(exarg_T *eap);
 void ex_finish(exarg_T *eap);
@@ -42,5 +43,4 @@
 char_u *may_prefix_autoload(char_u *name);
 char_u *autoload_name(char_u *name);
 int script_autoload(char_u *name, int reload);
-int sourcing_a_script(exarg_T *eap);
 /* vim: set ft=c : */