Fix the 3.12.1 compiler to install compiler-libs correctly inside oca…

…ml/lib/compiler-libs during the switch phase.

There are now 4 combinations of possible compiler-libs:

system 3.12.1 + utop = user must install local compiler-libs (tested with debian, works great)
switched 3.12.1 + utop = this patch installs correct compiler-libs (test here, works)
system 4.00 + utop = includes compiler-libs
switched 4.00 + utop = includes compiler-libs

Previously, the compiler-lib.3.12.1 package would install them inside .opam/3.12.1/lib/compiler-libs, which would break with the system compiler (where it is expected to be in the system ocamlc by config scripts).

This addresses OCamlPro/opam-repository#108 partially. We may also need to do:
* change compiler-libs.3.12.1 to detect if compiler-libs is installed with a system compiler, and prompt the user to take care of it if not (e.g. via `apt-get install ocaml-compiler-libs`)
* remove the compiler-libs packages as being unnecessary, as we can now assume they are always present. This solves an expensive build-time dependency with utop...
* remove other references in packages to compiler-libs and test them.

compilers/3.12.1.comp

@@ -1,7 +1,14 @@
 opam-version: "1"
 name: "3.12.1"
 src: "http://caml.inria.fr/pub/distrib/ocaml-3.12/ocaml-3.12.1.tar.gz"
-make: [ "world" "world.opt" ]
+build: [ 
+  ["./configure" "-prefix" "%{prefix}%"] 
+  ["make" "world"] 
+  ["make" "world.opt"] 
+  ["make" "install"] 
+  ["mkdir" "-p" "%{prefix}%/lib/ocaml/compiler-libs"]
+  ["cp" "-r" "typing" "parsing" "utils" "%{prefix}%/lib/ocaml/compiler-libs/"]
+]
 packages : [ "base-unix" "base-bigarray" "base-threads" ]
 env: [
   [ CAML_LD_LIBRARY_PATH = "%{lib}%/stublibs" ]

packages/utop.1.2.1/opam

@@ -8,4 +8,4 @@ build: [
 remove: [
   ["ocamlfind" "remove" "utop"]
 ]
-depends: ["ocamlfind" "compiler-libs" "zed" "lambda-term"]
+depends: ["ocamlfind" "zed" "lambda-term"]