Merge pull request #223 from william3/ocaml-update

ocaml-native : ocamlbuild was not looking for prefix-ocamlfind
Makefile: unexport various *TARGET* variables
Makefile: add settings.mk to failed log output
Makefile: add missing separator to find command
packages freetype libgpg_error libpng pcre: add prefixed *-config links
to be added to Makefile, to get extra debug info
temporary build for ocaml 4.02+dev