vim-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.
f273245f64

src/nvim/eval.lua

@@ -243,6 +243,8 @@ return {
     pow={args=2},
     prevnonblank={args=1},
     printf={args=varargs(1)},
+    prompt_setcallback={args={2, 2}},
+    prompt_setprompt={args={2, 2}},
     pum_getpos={},
     pumvisible={},
     py3eval={args=1},