Fixed common misspellings.

Mostly found by 'codespell'.

src/libcharon/encoding/payloads/encryption_payload.c

@@ -142,7 +142,7 @@ METHOD(payload_t, set_next_type, void,
 }
 
 /**
- * Compute the lenght of the whole payload
+ * Compute the length of the whole payload
  */
 static void compute_length(private_encryption_payload_t *this)
 {

src/libcharon/encoding/payloads/proposal_substructure.c

@@ -407,7 +407,7 @@ proposal_substructure_t *proposal_substructure_create_from_proposal(
 
 	this = (private_proposal_substructure_t*)proposal_substructure_create();
 
-	/* encryption algorithm is only availble in ESP */
+	/* encryption algorithm is only available in ESP */
 	enumerator = proposal->create_enumerator(proposal, ENCRYPTION_ALGORITHM);
 	while (enumerator->enumerate(enumerator, &alg, &key_size))
 	{

src/libcharon/encoding/payloads/transform_substructure.c

@@ -84,7 +84,7 @@ encoding_rule_t transform_substructure_encodings[] = {
 	{ U_INT_8,				offsetof(private_transform_substructure_t, transform_type)	},
 	/* 1 Reserved Byte */
 	{ RESERVED_BYTE,		offsetof(private_transform_substructure_t, reserved[1])		},
-	/* tranform ID is a number of 8 bit */
+	/* transform ID is a number of 8 bit */
 	{ U_INT_16,				offsetof(private_transform_substructure_t, transform_id)	},
 	/* Attributes are stored in a transform attribute,
 	   offset points to a linked_list_t pointer */

src/libcharon/encoding/payloads/transform_substructure.h

@@ -118,7 +118,7 @@ transform_substructure_t *transform_substructure_create(void);
  *
  * @param type			type of transform to create
  * @param id			transform id specifc for the transform type
- * @param key_length	key length for key lenght attribute, 0 to omit
+ * @param key_length	key length for key length attribute, 0 to omit
  * @return				transform_substructure_t object
  */
 transform_substructure_t *transform_substructure_create_type(