Prevent passwords from being recorded during text conversion

Prevent passwords from being recorded during text conversion

* doc/lispref/commands.texi (Misc Events): Document new value of
text-conversion-style.

* java/org/gnu/emacs/EmacsService.java (EmacsService)
<IC_MODE_PASSWORD>: New constant.

* java/org/gnu/emacs/EmacsView.java (onCreateInputConnection):
Set TYPE_TEXT_VARIATION_PASSWORD and IME_FLAG_FORCE_ASII if mode
is IC_MODE_PASSWORD.

* lisp/subr.el (read-passwd): Set text-conversion-style to
`password'.

* src/androidgui.h (enum android_ic_mode): New value
ANDROID_IC_MODE_PASSWORD.

* src/androidterm.c (android_reset_conversion): Handle
`password'.

* src/buffer.c (syms_of_buffer)
<&BVAR (current_buffer, text_conversion_style)>: Update doc
string.

* src/textconv.c (syms_of_textconv) <Qpassword>: New DEFSYM.
<Vtext_conversion_edits>: Fix typos in doc string.