Fix build for debian stretch

Fixes #182

CMakeLists.txt

@@ -2,6 +2,7 @@ cmake_minimum_required(VERSION 2.8.5)
 project(sway C)
 set(CMAKE_C_FLAGS "-g")
 set(CMAKE_C_STANDARD 99)
+SET(CMAKE_C_EXTENSIONS OFF)
 set(CMAKE_RUNTIME_OUTPUT_DIRECTORY "bin/")
 add_definitions("-Wall -Wextra -Wno-unused-parameter")
 set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} ${PROJECT_SOURCE_DIR}/CMake)

sway/commands.c

@@ -7,6 +7,7 @@
 #include <string.h>
 #include <unistd.h>
 #include <ctype.h>
+#include <sys/types.h>
 #include "stringop.h"
 #include "layout.h"
 #include "focus.h"

sway/main.c

@@ -3,6 +3,7 @@
 #include <stdbool.h>
 #include <wlc/wlc.h>
 #include <sys/wait.h>
+#include <sys/types.h>
 #include <signal.h>
 #include <getopt.h>
 #include "layout.h"