Add missing includes for mem_fn

Alc/backends/alsa.cpp

@@ -31,6 +31,7 @@
 #include <vector>
 #include <string>
 #include <algorithm>
+#include <functional>
 
 #include "alMain.h"
 #include "alu.h"

Alc/backends/dsound.cpp

@@ -38,6 +38,7 @@
 #include <string>
 #include <vector>
 #include <algorithm>
+#include <functional>
 
 #include "alMain.h"
 #include "alu.h"

Alc/backends/jack.cpp

@@ -27,6 +27,7 @@
 #include <memory.h>
 
 #include <thread>
+#include <functional>
 
 #include "alMain.h"
 #include "alu.h"

Alc/backends/null.cpp

@@ -29,6 +29,7 @@
 
 #include <chrono>
 #include <thread>
+#include <functional>
 
 #include "alMain.h"
 #include "alu.h"

Alc/backends/opensl.cpp

@@ -27,6 +27,7 @@
 #include <jni.h>
 
 #include <thread>
+#include <functional>
 
 #include "alMain.h"
 #include "alu.h"

Alc/backends/oss.cpp

@@ -41,6 +41,7 @@
 #include <vector>
 #include <string>
 #include <algorithm>
+#include <functional>
 
 #include "alMain.h"
 #include "alu.h"

Alc/backends/sndio.cpp

@@ -27,6 +27,7 @@
 #include <string.h>
 
 #include <thread>
+#include <functional>
 
 #include "alMain.h"
 #include "alu.h"

Alc/backends/solaris.cpp

@@ -36,6 +36,7 @@
 #include <math.h>
 
 #include <thread>
+#include <functional>
 
 #include "alMain.h"
 #include "alu.h"

Alc/backends/wasapi.cpp

@@ -45,6 +45,7 @@
 #include <vector>
 #include <string>
 #include <algorithm>
+#include <functional>
 
 #include "alMain.h"
 #include "alu.h"

Alc/backends/wave.cpp

@@ -30,6 +30,7 @@
 #include <chrono>
 #include <thread>
 #include <vector>
+#include <functional>
 
 #include "alMain.h"
 #include "alu.h"

Alc/backends/winmm.cpp

@@ -35,6 +35,7 @@
 #include <vector>
 #include <string>
 #include <algorithm>
+#include <functional>
 
 #include "alMain.h"
 #include "alu.h"