itrans input methods and motion keys

[Visuwesh <visuweshm@gmail.com>]

Dear all,

I'm posting this in emacs-devel instead of filing a bug report since I
want this to get a bit more attraction.  I'm also CCing Sameer Singh in
hopes that he can give insight into the non-Tamil side of things.

Currently, the itrans input methods are defined using the function
quail-define-indian-trans-package in lisp/leim/quail/indian.el.  This
function calls quail-define-package with a nil SIMPLE argument which
steals the commonly used motion keys C-f, C-b, C-n, C-p.  AFAICT from
what I read in quail a year or so ago, this argument is more useful for
the Chinese and the Japanese input methods but not so much for simple
IMs like the itrans one which only does transliteration.  Besides, even
if an IM has one to many translation i.e., if "a" can be translated to
"a->" and "a->>", and the SIMPLE argument is non-nil, one can use the
number keys to select the alternate translation.

Since the nil value of SIMPLE argument gives no real benefit in the case
of tamil-itrans IM, I would like to change it to t so that we can get
the motion keys back.  However, I have only ever used the Tamil IM and
thus have no idea about the other languages.  Then we can adjust the
quail-define-indian-trans-package function to pass a custom SIMPLE
argument instead.