bug#4387: read-file-name-completion-ignore-case has no effect in find-name-arg

[Juri Linkov]

The docstring of `find-name-arg' says that 
`read-file-name-completion-ignore-case'
defines its default value:

  ;;;###autoload
  (defcustom find-name-arg
    (if read-file-name-completion-ignore-case
        "-iname"
      "-name")
    "Argument used to specify file name pattern.
  If `read-file-name-completion-ignore-case' is non-nil, -iname is used so that
  find also ignores case. Otherwise, -name is used."
    :type 'string
    :group 'find-dired
    :version "22.2")

But there is no way to use "-iname" when `read-file-name-completion-ignore-case'
is customized to t because `find-name-arg' is autoloaded with the value "-name"
before

  (custom-set-variables
   '(read-file-name-completion-ignore-case t))

from .emacs sets the value of `read-file-name-completion-ignore-case'.

This also precludes from using -iname in `rgrep' that relies on `find-name-arg'.

-- 
Juri Linkov
http://www.jurta.org/emacs/