documentation: fix various spelling typos

Foudn with codespell.

Reference: https://github.com/codespell-project/codespell
Signed-off-by: Sami Kerola <kerolasa@iki.fi>

Documentation/README.maintainer

@@ -13,7 +13,7 @@ Use git commit --author 'Contributor <email>' when receiving changes that
 are not applicable as-is.  Not stealing contributions applies even if change
 has to be worked out, that is common case with commit message.
 
-Exeception to this rule is a change that is a good idea, but has to be
+Exception to this rule is a change that is a good idea, but has to be
 completely rewrote to be acceptable for the project.  In this case
 maintainer should attribute the person who gave the idea in commit message.
 

arping.c

@@ -652,7 +652,7 @@ static int check_device(struct run_state *ctl)
  * find_broadcast_address()
  *
  * This fills the device "broadcast address"
- * based on information found by check_device() funcion.
+ * based on information found by check_device() function.
  */
 static void find_broadcast_address(struct run_state *ctl)
 {

ping.c

@@ -82,7 +82,7 @@ static uint32_t route[10];
 
 static struct sockaddr_in whereto;	/* who to ping */
 static int optlen = 0;
-static int settos = 0;			/* Set TOS, Precendence or other QOS options */
+static int settos = 0;			/* Set TOS, Precedence or other QOS options */
 
 static int broadcast_pings = 0;
 

ping6_common.c

@@ -4,7 +4,7 @@
  *
  *	<roque@di.fc.ul.pt>
  *
- *	Original copyright notice included bellow
+ *	Original copyright notice included below
  */
 
 /*

ping_common.c

@@ -544,9 +544,7 @@ void setup(socket_st *sock)
 		disable_capability_admin();
 
 		if (ret == -1) {
-			/* we probably dont wanna exit since old kernels
-			 * dont support mark ..
-			*/
+			/* Do not exit, old kernels do not support mark. */
 			error(0, errno_save, _("Warning: Failed to set mark: %d"), mark);
 		}
 	}

rarpd.c

@@ -527,7 +527,7 @@ void serve_it(int fd)
 
 	/* Prepare reply. It is almost ready, we only
 	   replace ARP packet type, put our lladdr and
-	   IP address to source fileds,
+	   IP address to source fields,
 	   and fill target IP address.
 	 */
 	a->ar_op = htons(ARPOP_RREPLY);

rdisc.c

@@ -788,7 +788,7 @@ pr_pack(char *buf, int cc, struct sockaddr_in *from)
 				      pr_name(from->sin_addr),
 				      ntohs(rap->icmp_lifetime));
 
-		/* Check that at least one router address is a neighboor
+		/* Check that at least one router address is a neighbour
 		 * on the arriving link.
 		 */
 		for (i = 0; (unsigned)i < rap->icmp_num_addrs; i++) {
@@ -861,7 +861,7 @@ pr_pack(char *buf, int cc, struct sockaddr_in *from)
 				      pr_type((int)icp->type),
 				      pr_name(from->sin_addr));
 
-		/* Check that ip_src is either a neighboor
+		/* Check that ip_src is either a neighbour
 		 * on the arriving link or 0.
 		 */
 		sin.sin_family = AF_INET;