[lltx] lualibs depricated function

[Khaled Hosny]

As lualibs is mainly a repackaged ConTeXt libraries, the more close to
ConTeXt it is the more simpler the maintenance.

Currently, lualibs has some aliases to ConTeXt functions, as well as
implementations of deprecated/removed ones.

I checked other lua packages and found non of these functions is used,
expect of two fpath functions is luatextra that I just fixed, so I
decided to remove them completely.

Here is a list of the removed functions so that any one using them can
adapt his code:

* aliases, used the original function instead:
  fpath           = file
  fpath.split     = file.split_path
  lfs.is_readable = file.is_readable
  lfs.is_writable = file.is_writable

* removed functions, no direct replacement (they were removed in the
  first place mostly because the implementation is not robust):
  string:stripspaces
  lpeg.space
  lpeg.newline
  table.contains_value
  table.contains_key
  table.value_position
  table.key_position
  table.remove_key
  fpath.normalize_sep
  fpath.localize_sep
  table.starts_at

Regards,
 Khaled

-- 
 Khaled Hosny
 Arabic localiser and member of Arabeyes.org team
 Free font developer