Ignore -Waddress for alsaaudio.c

/usr/include/alsa/pcm.h contains:

#define snd_pcm_sw_params_alloca(ptr) do { assert(ptr); *ptr = (snd_pcm_sw_params_t *) alloca(snd_pcm_sw_params_sizeof()); memset(*ptr, 0, snd_pcm_sw_params_sizeof()); } while (0)

The assert generates: "error: the address of 'sw_params' will always
evaluate as 'true'" which combined with -Werror prevents alsaaudio.o
from being built with certain versions of GCC.

audio/alsaaudio.c

@@ -25,6 +25,10 @@
 #include "qemu-common.h"
 #include "audio.h"
 
+#if QEMU_GNUC_PREREQ(4, 3)
+#pragma GCC diagnostic ignored "-Waddress"
+#endif
+
 #define AUDIO_CAP "alsa"
 #include "audio_int.h"