stdcompat >= 12 needs autoconf

Otherwise it can fail with
```
=== ERROR while compiling stdcompat.18 =======================================#
 context              2.2.0~alpha~dev | linux/x86_64 | ocaml-base-compiler.4.14.1 | file:///home/opam/opam-repository
 path                 ~/.opam/4.14/.opam-switch/build/stdcompat.18
 command              ~/.opam/opam-init/hooks/sandbox.sh build make all
 exit-code            2
 env-file             ~/.opam/log/stdcompat-7-e9acad.env
 output-file          ~/.opam/log/stdcompat-7-e9acad.out
 CDPATH="${ZSH_VERSION+.}:" && cd . && /bin/bash /home/opam/.opam/4.14/.opam-switch/build/stdcompat.18/missing autoconf
 /home/opam/.opam/4.14/.opam-switch/build/stdcompat.18/missing: line 81: autoconf: command not found
 WARNING: 'autoconf' is missing on your system.
          You should only need it if you modified 'configure.ac',
          or m4 files included by it.
          The 'autoconf' program is part of the GNU Autoconf package:
          <http://www.gnu.org/software/autoconf/>
          It also requires GNU m4 and Perl in order to run:
          <http://www.gnu.org/software/m4/>
          <http://www.perl.org/>
 Makefile:1792: .depend: No such file or directory
 make: *** [Makefile:921: configure] Error 127
```
Signed-off-by: Marcello Seri <[email protected]>

Author: mseri

packages/stdcompat/stdcompat.12/opam

@@ -10,7 +10,7 @@ bug-reports: "https://github.com/thierry-martinez/stdcompat/issues"
 depends: [
   "ocaml" {>= "3.07" & < "4.11.0"}
 ]
-depopts: ["result" "seq" "uchar" "ocamlfind"]
+depopts: ["result" "seq" "uchar" "ocamlfind" "conf-autoconf"]
 build: [
   ["./configure" "--prefix=%{prefix}%"]
   [make]
@@ -23,4 +23,4 @@ url {
   checksum: [
     "sha512=5f699bb11b76be3c0a73172d58eed857f150717a5c868bc92f0a6f3bc084317b55c3f4e8bdfb451959feb9744831fd8be4e126afcc1c8dbca929a298ab427df9"
   ]
-}
+}

packages/stdcompat/stdcompat.13/opam

@@ -10,7 +10,7 @@ bug-reports: "https://github.com/thierry-martinez/stdcompat/issues"
 depends: [
   "ocaml" {>= "3.07" & < "4.11.0"}
 ]
-depopts: ["result" "seq" "uchar" "ocamlfind"]
+depopts: ["result" "seq" "uchar" "ocamlfind" "conf-autoconf"]
 build: [
   ["./configure" "--prefix=%{prefix}%"]
   [make]
@@ -23,4 +23,4 @@ url {
   checksum: [
     "sha512=baebc1d95c0aa4dabeb44cda63d2c52406e7b71622c45890dee02435b0feaecf05f94e4d710e0633ae75716154d2828e46322cd6e5803a7b14d80ed1098e492f"
   ]
-}
+}

packages/stdcompat/stdcompat.14/opam

@@ -10,7 +10,7 @@ bug-reports: "https://github.com/thierry-martinez/stdcompat/issues"
 depends: [
   "ocaml" {>= "3.07" & < "4.12.0"}
 ]
-depopts: [ "result" "seq" "uchar" "ocamlfind" ]
+depopts: [ "result" "seq" "uchar" "ocamlfind" "conf-autoconf" ]
 build: [
   ["./configure" "--prefix=%{prefix}%"]
   [make "all" "test" {with-test}]
@@ -23,4 +23,4 @@ url {
   checksum: [
     "sha512=787e2c625a25b25f166047563ae6428e682e2059610bfec3c3c3888d369ba91a80e03b1ab9f847108722d0797dbd9b71634b6ae51cc937aeb7964071c7d6dbe3"
   ]
-}
+}

packages/stdcompat/stdcompat.15/opam

@@ -10,7 +10,7 @@ bug-reports: "https://github.com/thierry-martinez/stdcompat/issues"
 depends: [
   "ocaml" {>= "3.08" & < "5.0"}
 ]
-depopts: [ "result" "seq" "uchar" "ocamlfind" ]
+depopts: [ "result" "seq" "uchar" "ocamlfind" "conf-autoconf" ]
 build: [
   ["./configure" "--prefix=%{prefix}%"]
   [make "all" "test" {with-test}]

packages/stdcompat/stdcompat.16/opam

@@ -10,7 +10,7 @@ bug-reports: "https://github.com/thierry-martinez/stdcompat/issues"
 depends: [
   "ocaml" {>= "3.08" & < "5.0"}
 ]
-depopts: [ "result" "seq" "uchar" "ocamlfind" ]
+depopts: [ "result" "seq" "uchar" "ocamlfind" "conf-autoconf" ]
 build: [
   ["./configure" "--prefix=%{prefix}%"]
   [make "all" "test" {with-test}]

packages/stdcompat/stdcompat.17/opam

@@ -10,7 +10,7 @@ bug-reports: "https://github.com/thierry-martinez/stdcompat/issues"
 depends: [
   "ocaml" {>= "3.08" & < "5.0"}
 ]
-depopts: [ "result" "seq" "uchar" "ocamlfind" ]
+depopts: [ "result" "seq" "uchar" "ocamlfind" "conf-autoconf" ]
 build: [
   ["./configure" "--prefix=%{prefix}%"]
   [make "all" "test" {with-test}]

packages/stdcompat/stdcompat.18/opam

@@ -10,7 +10,7 @@ bug-reports: "https://github.com/thierry-martinez/stdcompat/issues"
 depends: [
   "ocaml" {>= "3.08" & < "5.0"}
 ]
-depopts: [ "result" "seq" "uchar" "ocamlfind" ]
+depopts: [ "result" "seq" "uchar" "ocamlfind" "conf-autoconf" ]
 build: [
   ["./configure" "--prefix=%{prefix}%"]
   [make "all" "test" {with-test}]

packages/stdcompat/stdcompat.19/opam

@@ -11,7 +11,7 @@ depends: [
   "ocaml" {>= "3.07"}
   "dune" {>= "2.0"}
 ]
-depopts: [ "result" "seq" "uchar" "ocamlfind" ]
+depopts: [ "result" "seq" "uchar" "ocamlfind" "conf-autoconf" ]
 build: [
   ["dune" "subst"] {dev}
   ["dune" "build" "-p" name "-j" jobs]