inhibit-field-text-motion breaks comint-previous-input

[Ilya N. Golubev]

`comint.el' revision: 1.19.

`inhibit-field-text-motion' is defined to be user option, and it is
reasonable.  On request will describe cases when actually need to
change behavior controlled by it in comint mode buffers in course of
regular editing.  Can not do so safely.

If it is `t', `comint-previous-input', if previous command is C and
current process prompt is P, expect it to create buffer text

PC
  ^

without following newline.  (Point shown as `^'.)  So that C may be
edited and sent.  Instead, the following appears.

CP
 ^

If execute `comint-send-input' immediately, it sends P as command.  So
some parts of xemacs `comint' depend on user option value.