Compile using -std=c99 when available

Alc/backends/alsa.c

@@ -35,7 +35,7 @@ static const ALCchar alsaDevice[] = "ALSA Default";
 
 #ifdef HAVE_DYNLOAD
 static void *alsa_handle;
-#define MAKE_FUNC(f) static typeof(f) * p##f
+#define MAKE_FUNC(f) static __typeof(f) * p##f
 MAKE_FUNC(snd_strerror);
 MAKE_FUNC(snd_pcm_open);
 MAKE_FUNC(snd_pcm_close);

Alc/backends/portaudio.c

@@ -35,7 +35,7 @@ static const ALCchar pa_device[] = "PortAudio Default";
 
 #ifdef HAVE_DYNLOAD
 static void *pa_handle;
-#define MAKE_FUNC(x) static typeof(x) * p##x
+#define MAKE_FUNC(x) static __typeof(x) * p##x
 MAKE_FUNC(Pa_Initialize);
 MAKE_FUNC(Pa_Terminate);
 MAKE_FUNC(Pa_GetErrorText);

Alc/backends/pulseaudio.c

@@ -39,7 +39,7 @@
 
 #ifdef HAVE_DYNLOAD
 static void *pa_handle;
-#define MAKE_FUNC(x) static typeof(x) * p##x
+#define MAKE_FUNC(x) static __typeof(x) * p##x
 MAKE_FUNC(pa_context_unref);
 MAKE_FUNC(pa_sample_spec_valid);
 MAKE_FUNC(pa_frame_size);

CMakeLists.txt

@@ -100,10 +100,17 @@ CHECK_TYPE_SIZE("long" SIZEOF_LONG)
 CHECK_TYPE_SIZE("long long" SIZEOF_LONG_LONG)
 
 
+CHECK_C_COMPILER_FLAG(-std=c99 HAVE_STD_C99)
+IF(HAVE_STD_C99)
+    SET(CMAKE_C_FLAGS "-std=c99 ${CMAKE_C_FLAGS}")
+ENDIF()
+
+# TODO: Once we truly require C99, these restrict and inline checks should go
+# away. Currently they're needed to maintain MSVC compatibility.
 CHECK_C_SOURCE_COMPILES("int *restrict foo;
                          int main() {return 0;}" HAVE_RESTRICT)
 IF(NOT HAVE_RESTRICT)
-    # Slightly convoluted way to do this, because MSVC may barf is restrict is
+    # Slightly convoluted way to do this, because MSVC may barf if restrict is
     # defined to __restrict.
     CHECK_C_SOURCE_COMPILES("#define restrict __restrict
                              #include <stdlib.h>