patch 9.1.0934: hard to view an existing buffer in the preview window

Problem:  hard to view an existing buffer in the preview window
Solution: add the :pbuffer command (Yinzuo Jiang)

Similar as `:pedit` and `:buffer` command. `:pbuffer` edits buffer [N]
from the buffer list in the preview window.

`:pbuffer` can also open special buffer, for example terminal buffer.

closes: #16222

Signed-off-by: Yinzuo Jiang <jiangyinzuo@foxmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/ex_cmdidxs.h b/src/ex_cmdidxs.h
index 658f05e..0b13a6c 100644
--- a/src/ex_cmdidxs.h
+++ b/src/ex_cmdidxs.h
@@ -21,16 +21,16 @@
   /* n */ 308,
   /* o */ 328,
   /* p */ 340,
-  /* q */ 380,
-  /* r */ 383,
-  /* s */ 403,
-  /* t */ 473,
-  /* u */ 520,
-  /* v */ 531,
-  /* w */ 552,
-  /* x */ 566,
-  /* y */ 576,
-  /* z */ 577
+  /* q */ 381,
+  /* r */ 384,
+  /* s */ 404,
+  /* t */ 474,
+  /* u */ 521,
+  /* v */ 532,
+  /* w */ 553,
+  /* x */ 567,
+  /* y */ 577,
+  /* z */ 578
 };
 
 /*
@@ -56,7 +56,7 @@
   /* m */ {  1,  0,  0,  0,  7,  0,  0,  0,  0,  0, 10,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0, 16 },
   /* n */ {  0,  1,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  5,  8, 10,  0,  0,  0,  0,  0, 17,  0,  0,  0,  0,  0 },
   /* o */ {  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  1,  2,  5,  0,  0,  0,  0,  0,  0,  9,  0, 11,  0,  0,  0 },
-  /* p */ {  1,  0,  3,  0,  4,  0,  0,  0,  0,  0,  0,  0,  0,  0,  7,  9,  0,  0, 16, 17, 26,  0, 28,  0, 29,  0 },
+  /* p */ {  1,  3,  4,  0,  5,  0,  0,  0,  0,  0,  0,  0,  0,  0,  8, 10,  0,  0, 17, 18, 27,  0, 29,  0, 30,  0 },
   /* q */ {  2,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0 },
   /* r */ {  0,  0,  0,  0,  0,  0,  0,  0, 12,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0, 14, 19,  0,  0,  0,  0 },
   /* s */ {  2,  6, 15,  0, 19, 23,  0, 25, 26,  0,  0, 29, 31, 35, 39, 41,  0, 50,  0, 51,  0, 64, 65,  0, 66,  0 },
@@ -69,4 +69,4 @@
   /* z */ {  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0 }
 };
 
-static const int command_count = 594;
+static const int command_count = 595;