Add remove target for atdgen

This is to fix an issue when I was upgrading opam from
opam 1.1.2 to opam 1.2~beta4. See #2535.
+gettext.0.3.5, which should work on OCaml 4.02
restrict gettext.0.3.4 to <OCaml 4.02 due to format string incompatibility
Merge pull request #2544 from amirmc/atdgen

Add remove target for atdgen
Merge pull request #2543 from avsm/ncurses-depext

Add missing depext on curses
Merge pull request #2542 from avsm/extlib-camlp4

extlib depends on camlp4
Merge pull request #2541 from avsm/custom_printf-ocamlver

Restrict custom_printf to <4.02.0 OCaml where not supported
Merge pull request #2513 from planar/bson-deps

fix dependencies of "bson"
freetds.0.5.1: add depexts for OSX
OCaml 4.02
Merge pull request #2547 from jpdeplaix/master

OCaml 4.02
Merge pull request #2546 from Chris00/master

freetds.0.5.1: add depexts for OSX
Merge pull request #2545 from avsm/gettext-for-402

+gettext.0.3.5
Sync latest compiler pull requests
iocaml.0.4.6 for ocaml.4.02.0
iocamljs needs optcomp as well
iocaml-kernel needs lwt
Merge pull request #2548 from bactrian/sync-prs-1409353201

Sync OCaml compiler PRs
constrain old iocaml for 4.00.1 to work round ocp-build/index problems
utop 1.15