patch 8.1.2127: the indent.c file is a bit big

Problem:    The indent.c file is a bit big.
Solution:   Move C-indent code a a new cindent.c file.  Move other
            indent-related code to indent.c. (Yegappan Lakshmanan,
            closes #5031)
diff --git a/src/proto/edit.pro b/src/proto/edit.pro
index f1ab205..bc69b41 100644
--- a/src/proto/edit.pro
+++ b/src/proto/edit.pro
@@ -8,7 +8,6 @@
 void edit_unputchar(void);
 void display_dollar(colnr_T col);
 void undisplay_dollar(void);
-void change_indent(int type, int amount, int round, int replaced, int call_changed_bytes);
 void truncate_spaces(char_u *line);
 void backspace_until_column(int col);
 int get_literal(void);
@@ -30,6 +29,7 @@
 char_u *get_last_insert_save(void);
 void replace_push(int c);
 int replace_push_mb(char_u *p);
+void replace_join(int off);
 int hkmap(int c);
 int bracketed_paste(paste_mode_T mode, int drop, garray_T *gap);
 void ins_scroll(void);