firebird: pin to autoconf-2.71

Without the change `firebird` builds fail against `autconf-2.72` as:

    checking for cc_r... gcc
    ./configure: line 5894: syntax error near unexpected token `;;'
    ./configure: line 5894: `printf "%s\n" "$as_me: WARNING: --with-system-editline specified, not found. Using bundled editline" >&2;} ;;'

Upstream switched to `cmake` for new releases. Let's pin older ones to
`autoconf-2.71`.

pkgs/servers/firebird/default.nix

@@ -1,4 +1,4 @@
-{ lib, stdenv, fetchFromGitHub, libedit, autoreconfHook, zlib, unzip, libtommath, libtomcrypt, icu, superServer ? false }:
+{ lib, stdenv, fetchFromGitHub, libedit, autoreconfHook271, zlib, unzip, libtommath, libtomcrypt, icu, superServer ? false }:
 
 let base = {
   pname = "firebird";
@@ -13,7 +13,7 @@ let base = {
     maintainers = with maintainers; [ marcweber ];
   };
 
-  nativeBuildInputs = [ autoreconfHook ];
+  nativeBuildInputs = [ autoreconfHook271 ];
 
   buildInputs = [ libedit icu ];