packet_data_generator2: Add Makefile for GNU environment

The existing Makefile seems to suppose the BSD environment.
This patch renames existing Makefile into "Makefile.BSD" and
adds "Makefile.GNU" for GNU environment.

Usage Example:

 - For BSD environment
   $ make -f Makefile.BSD

 - For GNU environment
   $ make -f Makefile.GNU

Signed-off-by: IWASE Yusuke <iwase.yusuke0@gmail.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>

ryu/tests/packet_data_generator2/Makefile.GNU

@@ -0,0 +1,39 @@
+# Copyright (C) 2015 Nippon Telegraph and Telephone Corporation.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# OVS_SRC: openvswitch source directory
+# OVS_INC: openvswitch include directory
+# OVS_LIB: openvswitch library directory
+
+OVS_SRC=${HOME}/ovs
+OVS_INC=/usr/local/include/openvswitch
+OVS_LIB=/usr/local/lib
+
+CPPFLAGS=-std=gnu99 -I${OVS_SRC} -I${OVS_INC}
+LDFLAGS=-L${OVS_LIB} -Wl,-R${OVS_LIB} -lofproto -lopenvswitch -lpthread -lssl -lrt -lm -lcrypto
+
+PROG=gen
+NOMAN=
+
+all: generate
+
+gen: gen.c
+	${CC} $^ ${CPPFLAGS} ${LDFLAGS} -o $@
+
+generate: ${PROG}
+	./${PROG}
+
+clean:
+	rm ${PROG}