Backout changeset a1a89ff4ee31 (bug 762449) to disable jemalloc 3 for now.

configure.in

@@ -7176,9 +7176,6 @@ if test -z "$MOZ_MEMORY"; then
   esac
 else
   AC_DEFINE(MOZ_MEMORY)
-  if test -n "$NIGHTLY_BUILD"; then
-    MOZ_JEMALLOC3=1
-  fi
   if test -n "$MOZ_JEMALLOC3"; then
     AC_DEFINE(MOZ_JEMALLOC3)
   fi