DOC: Spelling fixes

[wt: this contains spelling fixes for both doc and code comments,
 should be backported, ignoring the parts which don't apply]
diff --git a/src/backend.c b/src/backend.c
index d34b5ec..57f811f 100644
--- a/src/backend.c
+++ b/src/backend.c
@@ -1019,7 +1019,7 @@
  *  - SF_ERR_PRXCOND if the connection has been limited by the proxy (maxconn)
  *  - SF_ERR_RESOURCE if a system resource is lacking (eg: fd limits, ports, ...)
  *  - SF_ERR_INTERNAL for any other purely internal errors
- * Additionnally, in the case of SF_ERR_RESOURCE, an emergency log will be emitted.
+ * Additionally, in the case of SF_ERR_RESOURCE, an emergency log will be emitted.
  * The server-facing stream interface is expected to hold a pre-allocated connection
  * in s->si[1].conn.
  */
diff --git a/src/checks.c b/src/checks.c
index 61d3768..8eb2c7a 100644
--- a/src/checks.c
+++ b/src/checks.c
@@ -1459,7 +1459,7 @@
  *  - SF_ERR_RESOURCE if a system resource is lacking (eg: fd limits, ports, ...)
  *  - SF_ERR_INTERNAL for any other purely internal errors
  *  - SF_ERR_CHK_PORT if no port could be found to run a health check on an AF_INET* socket
- * Additionnally, in the case of SF_ERR_RESOURCE, an emergency log will be emitted.
+ * Additionally, in the case of SF_ERR_RESOURCE, an emergency log will be emitted.
  * Note that we try to prevent the network stack from sending the ACK during the
  * connect() when a pure TCP check is used (without PROXY protocol).
  */
@@ -1841,7 +1841,7 @@
  *  - SF_ERR_PRXCOND if the connection has been limited by the proxy (maxconn)
  *  - SF_ERR_RESOURCE if a system resource is lacking (eg: fd limits, ports, ...)
  *  - SF_ERR_INTERNAL for any other purely internal errors
- * Additionnally, in the case of SF_ERR_RESOURCE, an emergency log will be emitted.
+ * Additionally, in the case of SF_ERR_RESOURCE, an emergency log will be emitted.
  *
  * Blocks and then unblocks SIGCHLD
  */
@@ -2767,7 +2767,7 @@
 			 *  - SF_ERR_PRXCOND if the connection has been limited by the proxy (maxconn)
 			 *  - SF_ERR_RESOURCE if a system resource is lacking (eg: fd limits, ports, ...)
 			 *  - SF_ERR_INTERNAL for any other purely internal errors
-			 * Additionnally, in the case of SF_ERR_RESOURCE, an emergency log will be emitted.
+			 * Additionally, in the case of SF_ERR_RESOURCE, an emergency log will be emitted.
 			 * Note that we try to prevent the network stack from sending the ACK during the
 			 * connect() when a pure TCP check is used (without PROXY protocol).
 			 */
diff --git a/src/proto_tcp.c b/src/proto_tcp.c
index f1e3b60..f6d8ca1 100644
--- a/src/proto_tcp.c
+++ b/src/proto_tcp.c
@@ -267,7 +267,7 @@
  *  - SF_ERR_PRXCOND if the connection has been limited by the proxy (maxconn)
  *  - SF_ERR_RESOURCE if a system resource is lacking (eg: fd limits, ports, ...)
  *  - SF_ERR_INTERNAL for any other purely internal errors
- * Additionnally, in the case of SF_ERR_RESOURCE, an emergency log will be emitted.
+ * Additionally, in the case of SF_ERR_RESOURCE, an emergency log will be emitted.
  *
  * The connection's fd is inserted only when SF_ERR_NONE is returned, otherwise
  * it's invalid and the caller has nothing to do.
diff --git a/src/proto_uxst.c b/src/proto_uxst.c
index b2a7fe2..5c8f9d4 100644
--- a/src/proto_uxst.c
+++ b/src/proto_uxst.c
@@ -407,7 +407,7 @@
  *  - SF_ERR_PRXCOND if the connection has been limited by the proxy (maxconn)
  *  - SF_ERR_RESOURCE if a system resource is lacking (eg: fd limits, ports, ...)
  *  - SF_ERR_INTERNAL for any other purely internal errors
- * Additionnally, in the case of SF_ERR_RESOURCE, an emergency log will be emitted.
+ * Additionally, in the case of SF_ERR_RESOURCE, an emergency log will be emitted.
  *
  * The connection's fd is inserted only when SF_ERR_NONE is returned, otherwise
  * it's invalid and the caller has nothing to do.