Make volume component work on FreeBSD

- Edit compile instructions
- Reuse OpenBSD sndio implementation

components/volume.c

@@ -7,7 +7,7 @@
 
 #include "../util.h"
 
-#if defined(__OpenBSD__)
+#if defined(__OpenBSD__) | defined(__FreeBSD__)
 	#include <sys/queue.h>
 	#include <poll.h>
 	#include <sndio.h>

config.def.h

@@ -59,7 +59,7 @@ static const char unknown_str[] = "n/a";
  * uptime              system uptime                   NULL
  * username            username of current user        NULL
  * vol_perc            OSS/ALSA volume in percent      mixer file (/dev/mixer)
- *                                                     NULL on OpenBSD
+ *                                                     NULL on OpenBSD/FreeBSD
  * wifi_perc           WiFi signal in percent          interface name (wlan0)
  * wifi_essid          WiFi ESSID                      interface name (wlan0)
  */

config.mk

@@ -15,7 +15,7 @@ CPPFLAGS = -I$(X11INC) -D_DEFAULT_SOURCE
 CFLAGS   = -std=c99 -pedantic -Wall -Wextra -Os
 LDFLAGS  = -L$(X11LIB) -s
 # OpenBSD: add -lsndio
-# FreeBSD: add -lkvm
+# FreeBSD: add -lkvm -lsndio
 LDLIBS   = -lX11
 
 # compiler and linker