mongodb: Fix default storage engine on i686

MongoDB will refuse to start on i686 because the default database engine
"wiredTiger" doesn't support it. To reduce user annoyance, the default
engine should be changed to the pre-3.0 engine "mmapv1".

Fedora have also patched it:
http://pkgs.fedoraproject.org/cgit/rpms/mongodb.git/commit/?id=b64d6b3337bffdeea0b7fa530ea02b977c364e08

Changed files
+5
pkgs
servers
nosql
mongodb
+5
pkgs/servers/nosql/mongodb/default.nix
···
substituteInPlace src/third_party/s2/s2cap.cc --replace drem remainder
substituteInPlace src/third_party/s2/s2latlng.cc --replace drem remainder
substituteInPlace src/third_party/s2/s2latlngrect.cc --replace drem remainder
+
'' + stdenv.lib.optionalString stdenv.isi686 ''
+
+
# don't fail by default on i686
+
substituteInPlace src/mongo/db/storage/storage_options.h \
+
--replace 'engine("wiredTiger")' 'engine("mmapv1")'
'';
buildPhase = ''