php: drop 7.1

PHP 7.1 is currently on life support, as in only recieving security related patches.

This will only continue until: 2019-12-01

This date are in the middle of the 19.09 lifecycle. So it would be
nice to not have it in the 19.09 stable release. Dropping it now would
also result in less maintanance in updating them.

The death dates can be seen on following links:
 - https://endoflife.date/php
 - https://php.net/supported-versions.php
 - https://en.wikipedia.org/wiki/PHP#Release_history

pkgs/servers/http/unit/default.nix

@@ -1,6 +1,5 @@
 { stdenv, fetchFromGitHub, which
 , withPython ? true, python
-, withPHP71 ? false, php71
 , withPHP72 ? true, php72
 , withPHP73 ? false, php73
 , withPerl ? true, perl
@@ -30,7 +29,6 @@ stdenv.mkDerivation rec {
 
   buildInputs = [ ]
     ++ optional withPython python
-    ++ optional withPHP71 php71
     ++ optional withPHP72 php72
     ++ optional withPHP73 php73
     ++ optional withPerl perl
@@ -51,7 +49,6 @@ stdenv.mkDerivation rec {
 
   postConfigure = ''
     ${optionalString withPython     "./configure python  --module=python    --config=${python}/bin/python-config  --lib-path=${python}/lib"}
-    ${optionalString withPHP71      "./configure php     --module=php71     --config=${php71.dev}/bin/php-config  --lib-path=${php71}/lib"}
     ${optionalString withPHP72      "./configure php     --module=php72     --config=${php72.dev}/bin/php-config  --lib-path=${php72}/lib"}
     ${optionalString withPHP73      "./configure php     --module=php73     --config=${php73.dev}/bin/php-config  --lib-path=${php73}/lib"}
     ${optionalString withPerl       "./configure perl    --module=perl      --perl=${perl}/bin/perl"}