Mark usage function as __dead2 in programs where it does not return

In most cases, usage does not return, so mark them as __dead2. For the
cases where they do return, they have not been marked __dead2.

Reviewed by: imp
Pull Request: https://github.com/freebsd/freebsd-src/pull/735

usr.sbin/accton/accton.c

@@ -50,7 +50,7 @@ __FBSDID("$FreeBSD$");
 #include <string.h>
 #include <unistd.h>
 
-static void usage(void);
+static void usage(void) __dead2;
 
 int
 main(int argc, char *argv[])

usr.sbin/arp/arp.c

@@ -90,7 +90,7 @@ static void nuke_entries(uint32_t ifindex, struct in_addr addr);
 static int print_entries(uint32_t ifindex, struct in_addr addr);
 
 static int delete(char *host);
-static void usage(void);
+static void usage(void) __dead2;
 static int set(int argc, char **argv);
 static int get(char *host);
 static int file(char *name);

usr.sbin/bluetooth/bthidcontrol/bthidcontrol.c

@@ -48,7 +48,7 @@
 static int do_bthid_command(bdaddr_p bdaddr, int argc, char **argv);
 static struct bthid_command * find_bthid_command(char const *command, struct bthid_command *category);
 static void print_bthid_command(struct bthid_command *category);
-static void usage(void);
+static void usage(void) __dead2;
 
 int32_t hid_sdp_query(bdaddr_t const *local, bdaddr_t const *remote, int32_t *error);
 

usr.sbin/bluetooth/btpand/btpand.c

@@ -72,9 +72,9 @@ static const struct {
 	{ "GN",	  SDP_SERVICE_CLASS_GN,   "Group Network"		  },
 };
 
-static void main_exit(int);
+static void main_exit(int) __dead2;
 static void main_detach(void);
-static void usage(void);
+static void usage(void) __dead2;
 
 int
 main(int argc, char *argv[])

usr.sbin/boot0cfg/boot0cfg.c

@@ -107,7 +107,7 @@ static int boot0bs(const u_int8_t *);
 static void stropt(const char *, int *, int *);
 static int argtoi(const char *, int, int, int);
 static int set_bell(u_int8_t *, int, int);
-static void usage(void);
+static void usage(void) __dead2;
 
 static unsigned vol_id[5];	/* 4 plus 1 for flag */
 

usr.sbin/bootparamd/bootparamd/main.c

@@ -39,7 +39,7 @@ const char *bootpfile = "/etc/bootparams";
 
 static struct sockaddr_in my_addr;
 
-static void usage(void);
+static void usage(void) __dead2;
 
 int
 main(int argc, char **argv)

usr.sbin/bootparamd/callbootd/callbootd.c

@@ -30,7 +30,7 @@ static char cln[MAX_MACHINE_NAME+1];
 static char dmn[MAX_MACHINE_NAME+1];
 static char path[MAX_PATH_LEN+1];
 
-static void usage(void);
+static void usage(void) __dead2;
 int printgetfile(bp_getfile_res *);
 int printwhoami(bp_whoami_res *);
 

usr.sbin/btxld/btxld.c

@@ -127,7 +127,7 @@ static unsigned int optfmt(const char *);
 static uint32_t optaddr(const char *);
 static int optpage(const char *, int);
 static void Warn(const char *, const char *, ...);
-static void usage(void);
+static void usage(void) __dead2;
 
 /*
  * A link editor for BTX clients.

usr.sbin/chroot/chroot.c

@@ -58,7 +58,7 @@ __FBSDID("$FreeBSD$");
 #include <string.h>
 #include <unistd.h>
 
-static void usage(void);
+static void usage(void) __dead2;
 
 int
 main(int argc, char *argv[])

usr.sbin/ckdist/ckdist.c

@@ -86,7 +86,7 @@ static const char *stripath(const char *path);
 static int distfile(const char *path);
 static int disttype(const char *name);
 static int fail(const char *path, const char *msg);
-static void usage(void);
+static void usage(void) __dead2;
 
 int
 main(int argc, char *argv[])

usr.sbin/crunch/crunchide/crunchide.c

@@ -76,7 +76,7 @@ __FBSDID("$FreeBSD$");
 
 static const char *pname = "crunchide";
 
-static void usage(void);
+static void usage(void) __dead2;
 
 static void add_to_keep_list(char *symbol);
 static void add_file_to_keep_list(char *filename);

usr.sbin/edquota/edquota.c

@@ -110,7 +110,7 @@ struct quotause *getprivs(long, int, char *);
 void putprivs(long, struct quotause *);
 int readprivs(struct quotause *, char *);
 int readtimes(struct quotause *, char *);
-static void usage(void);
+static void usage(void) __dead2;
 int writetimes(struct quotause *, int, int);
 int writeprivs(struct quotause *, int, char *, int);
 

usr.sbin/efitable/efitable.c

@@ -48,7 +48,7 @@ __FBSDID("$FreeBSD$");
 
 static void efi_table_print_esrt(const void *data);
 static void efi_table_print_prop(const void *data);
-static void usage(void);
+static void usage(void) __dead2;
 
 struct efi_table_op {
 	char name[TABLE_MAX_LEN];