fix for ocaml 4.01 / split META-file

1) fix for ocaml 4.01beta
  ( see http://caml.inria.fr/mantis/view.php?id=5119 / https://github.com/ocaml/ocaml/commit/b570a86fa735ada41475a189ad26a61d27f5a101  for changes)
2) Split the META file in two sections:

* one section for preprocessor 'mikmatch_pcre' (canonical way would be mikmatch_pcre.syntax, but this would break existing makefiles)
* one for the runtime part 'mikmatch_pcre.lib'

One section, that you can pass to ocamlfind for linking; one section for preprocessing.  This simplifies build instructions, if you use different (incompatible) camlp4-extensions.


(previous Makefile update didn't work. I've therefore opened a new request )