patch 8.2.3787: no proper formatting of a C line comment after a statement

Problem:    No proper formatting of a C line comment after a statement.
Solution:   Find the start of the line comment, insert the comment leader and
            indent the comment properly.
diff --git a/src/proto/change.pro b/src/proto/change.pro
index b1aa9d5..502b285 100644
--- a/src/proto/change.pro
+++ b/src/proto/change.pro
@@ -27,7 +27,7 @@
 int del_char(int fixpos);
 int del_chars(long count, int fixpos);
 int del_bytes(long count, int fixpos_arg, int use_delcombine);
-int open_line(int dir, int flags, int second_line_indent);
+int open_line(int dir, int flags, int second_line_indent, int *did_do_comment);
 int truncate_line(int fixpos);
 void del_lines(long nlines, int undo);
 /* vim: set ft=c : */