tags: Unify emacs and exuberant rules

The emacs rules were constantly lagging behind the exuberant ones. Use a
single set of rules for both, to make the script easier to maintain.
The language understood by both tools is basic regular expression with
some limitations, which are documented in a comment. To be able to store
the rules in an array and easily iterate over it, the script requires
bash now. In the exuberant case, the change fixes some false matches in
<linux/page-flags.h> and also some too greedy matches in the arguments
of the DECLARE_*/DEFINE_* macros. In the emacs case, several previously
not working rules are matching now. Tested with these versions of the
tools:

  Exuberant Ctags 5.8, Copyright (C) 1996-2009 Darren Hiebert
  etags (GNU Emacs 24.5)

Signed-off-by: Michal Marek <mmarek@suse.com>