Literal quotations for OCaml 4.11

[thierry-martinez]

This pull-request implements (partially) #83 on top of #82 for OCaml 4.11.

This PR introduces a test set for quoting literals.

[kit-ty-kate]

This PR seems to make several packages not compile. For instance:

• ocaml-monadic

- + /home/opam/.opam/4.11.0+trunk/bin/ocamlfind ocamldep -package ppx_tools.metaquot -package ppx_tools -package compiler-libs.common -modules src/ocaml_monadic.ml > src/ocaml_monadic.ml.depends
- File "src/ocaml_monadic.ml", line 13, characters 17-21:
- 13 |       | [%expr [%bind [%e? expr]]] ->
-                       ^^^^
- Error: Pattern expected.
- File "src/ocaml_monadic.ml", line 1:
- Error: Error while running external preprocessor
- Command line: /home/opam/.opam/4.11.0+trunk/lib/ppx_tools/metaquot/./ppx.exe --as-ppx '/tmp/camlppx5bc5ec' '/tmp/camlppx0de052'

• ppx_defer

#=== ERROR while compiling ppx_defer.0.1.0 ====================================#
# context              2.1.0~alpha | linux/x86_64 | ocaml-variants.4.11.0+trunk | file:///home/opam/opam-repository
# path                 ~/.opam/4.11.0+trunk/.opam-switch/build/ppx_defer.0.1.0
# command              ~/.opam/4.11.0+trunk/bin/ocaml pkg/build.ml native=true native-dynlink=true
# exit-code            10
# env-file             ~/.opam/log/ppx_defer-6-9088e2.env
# output-file          ~/.opam/log/ppx_defer-6-9088e2.out
### output ###
# [...]
# ocamlfind ocamlopt unix.cmxa -I /home/opam/.opam/4.11.0+trunk/lib/ocamlbuild /home/opam/.opam/4.11.0+trunk/lib/ocamlbuild/ocamlbuildlib.cmxa -linkpkg myocamlbuild.ml /home/opam/.opam/4.11.0+trunk/lib/ocamlbuild/ocamlbuild.cmx -o myocamlbuild
# ocamlfind ocamldep -package ppx_tools.metaquot -modules src/ppx_defer.ml > src/ppx_defer.ml.depends
# + ocamlfind ocamldep -package ppx_tools.metaquot -modules src/ppx_defer.ml > src/ppx_defer.ml.depends
# File "src/ppx_defer.ml", line 39, characters 19-24:
# 39 |         | [%expr [%defer [%e? later]] ; [%e? now]] ->
#                         ^^^^^
# Error: Pattern expected.
# File "src/ppx_defer.ml", line 1:
# Error: Error while running external preprocessor
# Command line: /home/opam/.opam/4.11.0+trunk/lib/ppx_tools/metaquot/./ppx.exe --as-ppx '/tmp/camlppx4f2fe6' '/tmp/camlppx8f3df8'
# 
# Command exited with code 2.

[kit-ty-kate]

Closing as ppx_tools is deprecated in favour of ppxlib in its everyday usage.