Bug#341203: minor correction to line-number

[YANG Shouxun <yang.shx@fltrp.com>]

According to the documentation to count-lines, reproduced below:

count-lines is a compiled Lisp function in `simple.el'.
(count-lines START END)

Return number of lines between START and END.
This is usually the number of newlines between them,
but can be one more if START is not equal to END
and the greater of them is not at the start of a line.

We'd better move point to the beginning of line before calling count-lines.
It also can be nice if we define line-number somewhere:

(defun line-number ()
  (if tuareg-with-xemacs
      (line-number)
    (1+ (count-lines 1
        (save-excursion (progn (beginning-of-line) (point)))))))

Anyway, this does not stop tuareg from raising an error scanning gdome.mli, 
which seems to be wrong. I don't understand why tuareg raises scanning error 
at line 615. The ocaml-mode certainly goes well with gdome.mli. Should I file 
another bug report?