Core: added autotest for UDP segmentation offloading.

auto/os/linux

diff --git a/auto/os/linux b/auto/os/linux
index 74b5870..0ae701f 100644
--- a/auto/os/linux
+++ b/auto/os/linux
@@ -232,4 +232,20 @@
 ngx_include="sys/vfs.h";     . auto/include
 
 
+# UDP segmentation offloading
+
+ngx_feature="UDP_SEGMENT"
+ngx_feature_name="NGX_HAVE_UDP_SEGMENT"
+ngx_feature_run=no
+ngx_feature_incs="#include <sys/socket.h>
+                  #include <stdint.h>
+                  #include <netinet/udp.h>"
+ngx_feature_path=
+ngx_feature_libs=
+ngx_feature_test="socklen_t optlen = sizeof(int);
+                  int val;
+                  getsockopt(0, SOL_UDP, UDP_SEGMENT, &val, &optlen)"
+. auto/feature
+
+
 CC_AUX_FLAGS="$cc_aux_flags -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64"

src/os/unix/ngx_linux_config.h

diff --git a/src/os/unix/ngx_linux_config.h b/src/os/unix/ngx_linux_config.h
index 3036cae..88fef47 100644
--- a/src/os/unix/ngx_linux_config.h
+++ b/src/os/unix/ngx_linux_config.h
@@ -103,6 +103,10 @@
 #include <linux/capability.h>
 #endif
 
+#if (NGX_HAVE_UDP_SEGMENT)
+#include <netinet/udp.h>
+#endif
+
 
 #define NGX_LISTEN_BACKLOG        511