make etags use -r and -l options that are not always available

[Bill Allombert <allomber@math.u-bordeaux.fr>]

Hello PARI-dev,

make etags fails if etags is 

Exuberant Ctags 5.2.2, Copyright (C) 1996-2001 Darren Hiebert
  Compiled: Feb 17 2002, 15:21:28
  Addresses: <dhiebert@users.sourceforge.net>, http://ctags.sourceforge.net
  Optional compiled features: +wildcards, +regex

This is due to the use of the -r and -l options that are not supported.

%LANG=C make etags
cd src; sh make_emacs_tags
etags: Unknown option: -r
etags: Unknown option: -l
etags: Unknown option: -l
etags: Unknown option: -l
Can't open TAGS.tmp: No such file or directory.

Cheers,
Bill.