Fix all spelling errors found by codespell.

NEWS

@@ -341,7 +341,7 @@ Version 1.0.9                Dec 26 2008
 
  * Enable path MTU discovery by default.
 
- * Fixed a memory leak that occured when connections were closed.
+ * Fixed a memory leak that occurred when connections were closed.
 
  Thanks to Max Rijevski for his contributions to this version of tinc.
 

doc/CONNECTIVITY

@@ -26,7 +26,7 @@ share the same information. It will also almost completely prevent information
 from looping, because "new" information that is already known is ignored and
 not forwarded any further. However, since information can also be deleted
 there's the possibility of a looping sequence of add/delete messages. This is
-resolved by additionaly adding a unique identifier to each broadcasted message.
+resolved by additionally adding a unique identifier to each broadcasted message.
 Messages are dropped if the same message with that identifier has already been
 seen.
 

doc/PROTOCOL

@@ -33,7 +33,7 @@ is pretty basic.
 A data packet can only be sent if the encryption key, cipher and digest are
 known to both parties, and the connection is activated. If the encryption key
 is not known, a request is sent to the destination using the meta connection to
-retreive it.
+retrieve it.
 
 0   1   2   3   4   5   6   7   ...   97  98  99  100
 |     seqno     |         data        |     MAC       |
@@ -59,7 +59,7 @@ daemon and to read and write requests by hand, provided that one
 understands the numeric codes sent.
 
 The authentication scheme is described in the SECURITY2 file. After a
-succesful authentication, the server and the client will exchange all the
+successful authentication, the server and the client will exchange all the
 information about other tinc daemons and subnets they know of, so that both
 sides (and all the other tinc daemons behind them) have their information
 synchronised.

doc/SECURITY2

@@ -61,7 +61,7 @@ client  CHAL_REPLY 816a86
 server  CHAL_REPLY 928ffe
                       +-> 160 bits SHA1 of H1
 
-After the correct challenge replies are recieved, both ends have proved
+After the correct challenge replies are received, both ends have proved
 their identity. Further information is exchanged.
 
 client  ACK 655 123 0

src/event.c

@@ -56,7 +56,7 @@ void expire_events(void) {
 	time_t diff;
 
 	/*
-	 * Make all events appear expired by substracting the difference between
+	 * Make all events appear expired by subtracting the difference between
 	 * the expiration time of the last event and the current time.
 	 */
 

src/protocol_misc.c

@@ -49,7 +49,7 @@ bool send_pong(connection_t *c) {
 bool pong_h(connection_t *c) {
 	c->status.pinged = false;
 
-	/* Succesful connection, reset timeout if this is an outgoing connection. */
+	/* Successful connection, reset timeout if this is an outgoing connection. */
 
 	if(c->outgoing) {
 		c->outgoing->timeout = 0;