Fixed compilation with -DNGX_DEBUG_MALLOC on FreeBSD 10.

After jemalloc 3.0.0 import there is no _malloc_options symbol, it has
been replaced with the malloc_conf one with a different syntax.

src/os/unix/ngx_freebsd_init.c

diff --git a/src/os/unix/ngx_freebsd_init.c b/src/os/unix/ngx_freebsd_init.c
index 57af44a..aeeceaf 100644
--- a/src/os/unix/ngx_freebsd_init.c
+++ b/src/os/unix/ngx_freebsd_init.c
@@ -76,9 +76,9 @@
 {
 #if (NGX_DEBUG_MALLOC)
 
-#if __FreeBSD_version >= 500014
+#if __FreeBSD_version >= 500014 && __FreeBSD_version < 1000011
     _malloc_options = "J";
-#else
+#elif __FreeBSD_version < 500014
     malloc_options = "J";
 #endif