nghttp2: 1.8.0 -> 1.9.2, unify with libnghttp2, and use multiple outputs

Note: I ignored the C++ libraries, but it appears we're not currently
using them. Once we do, we'll probably want to put them in a separate
output as well (to prevent non-C++ users from depending on Boost).

pkgs/servers/http/apache-httpd/2.4.nix

@@ -1,7 +1,7 @@
 { stdenv, fetchurl, perl, zlib, apr, aprutil, pcre, libiconv
 , proxySupport ? true
 , sslSupport ? true, openssl
-, http2Support ? true, libnghttp2
+, http2Support ? true, nghttp2
 , ldapSupport ? true, openldap
 , libxml2Support ? true, libxml2
 , luaSupport ? false, lua5
@@ -13,7 +13,7 @@ in
 
 assert sslSupport -> aprutil.sslSupport && openssl != null;
 assert ldapSupport -> aprutil.ldapSupport && openldap != null;
-assert http2Support -> libnghttp2 != null;
+assert http2Support -> nghttp2 != null;
 
 stdenv.mkDerivation rec {
   version = "2.4.18";
@@ -32,7 +32,7 @@ stdenv.mkDerivation rec {
     optional sslSupport openssl ++
     optional ldapSupport openldap ++    # there is no --with-ldap flag
     optional libxml2Support libxml2 ++
-    optional http2Support libnghttp2 ++
+    optional http2Support nghttp2 ++
     optional stdenv.isDarwin libiconv;
 
   patchPhase = ''
@@ -59,7 +59,7 @@ stdenv.mkDerivation rec {
     --enable-cgi
     ${optionalString proxySupport "--enable-proxy"}
     ${optionalString sslSupport "--enable-ssl"}
-    ${optionalString http2Support "--enable-http2 --with-nghttp2=${libnghttp2}"}
+    ${optionalString http2Support "--enable-http2 --with-nghttp2"}
     ${optionalString luaSupport "--enable-lua --with-lua=${lua5}"}
     ${optionalString libxml2Support "--with-libxml2=${libxml2.dev}/include/libxml2"}
     --docdir=$(doc)/share/doc