patch 8.1.0027: difficult to make a plugin that feeds a line to a job

Problem:    Difficult to make a plugin that feeds a line to a job.
Solution:   Add the nitial code for the "prompt" buftype.
diff --git a/src/proto/buffer.pro b/src/proto/buffer.pro
index 59bb2c2..9e63fb6 100644
--- a/src/proto/buffer.pro
+++ b/src/proto/buffer.pro
@@ -59,6 +59,7 @@
 int bt_quickfix(buf_T *buf);
 int bt_terminal(buf_T *buf);
 int bt_help(buf_T *buf);
+int bt_prompt(buf_T *buf);
 int bt_nofile(buf_T *buf);
 int bt_dontwrite(buf_T *buf);
 int bt_dontwrite_msg(buf_T *buf);
diff --git a/src/proto/channel.pro b/src/proto/channel.pro
index 8d26158..e6c9508 100644
--- a/src/proto/channel.pro
+++ b/src/proto/channel.pro
@@ -71,4 +71,5 @@
 void job_info(job_T *job, dict_T *dict);
 void job_info_all(list_T *l);
 int job_stop(job_T *job, typval_T *argvars, char *type);
+void invoke_prompt_callback(void);
 /* vim: set ft=c : */
diff --git a/src/proto/edit.pro b/src/proto/edit.pro
index 1f9e5b7..9ba7164 100644
--- a/src/proto/edit.pro
+++ b/src/proto/edit.pro
@@ -1,6 +1,8 @@
 /* edit.c */
 int edit(int cmdchar, int startln, long count);
 void edit_putchar(int c, int highlight);
+char_u *prompt_text(void);
+int prompt_curpos_editable(void);
 void edit_unputchar(void);
 void display_dollar(colnr_T col);
 void change_indent(int type, int amount, int round, int replaced, int call_changed_bytes);
diff --git a/src/proto/ops.pro b/src/proto/ops.pro
index 13e063e..01df56f 100644
--- a/src/proto/ops.pro
+++ b/src/proto/ops.pro
@@ -1,6 +1,7 @@
 /* ops.c */
 int get_op_type(int char1, int char2);
 int op_on_lines(int op);
+int op_is_change(int op);
 int get_op_char(int optype);
 int get_extra_op_char(int optype);
 void op_shift(oparg_T *oap, int curs_top, int amount);