Rename aead_chacha20_poly1305 to chachapoly

While the old name is explicit and aligned with the RFC, it's also very long,
so with the mbedtls_ prefix prepended we get a 31-char prefix to each
identifier, which quickly conflicts with our 80-column policy.

The new name is shorter, it's what a lot of people use when speaking about
that construction anyway, and hopefully should not introduce confusion at
it seems unlikely that variants other than 20/1305 be standardised in the
foreseeable future.
diff --git a/library/cipher_wrap.c b/library/cipher_wrap.c
index d8c5f06..5c80828 100644
--- a/library/cipher_wrap.c
+++ b/library/cipher_wrap.c
@@ -33,8 +33,8 @@
 
 #include "mbedtls/cipher_internal.h"
 
-#if defined(MBEDTLS_AEAD_CHACHA20_POLY1305_C)
-#include "mbedtls/aead_chacha20_poly1305.h"
+#if defined(MBEDTLS_CHACHAPOLY_C)
+#include "mbedtls/chachapoly.h"
 #endif
 
 #if defined(MBEDTLS_AES_C)
@@ -1356,40 +1356,41 @@
 };
 #endif /* MBEDTLS_CHACHA20_C */
 
-#if defined(MBEDTLS_AEAD_CHACHA20_POLY1305_C)
+#if defined(MBEDTLS_CHACHAPOLY_C)
 
-static int aead_chacha20_poly1305_setkey_wrap( void *ctx, const unsigned char *key,
-                                               unsigned int key_bitlen )
+static int chachapoly_setkey_wrap( void *ctx,
+                                   const unsigned char *key,
+                                   unsigned int key_bitlen )
 {
     if( key_bitlen != 256U )
         return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
 
-    if ( 0 != mbedtls_aead_chacha20_poly1305_setkey( (mbedtls_aead_chacha20_poly1305_context*)ctx, key ) )
+    if ( 0 != mbedtls_chachapoly_setkey( (mbedtls_chachapoly_context*)ctx, key ) )
         return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
 
     return( 0 );
 }
 
-static void * aead_chacha20_poly1305_ctx_alloc( void )
+static void * chachapoly_ctx_alloc( void )
 {
-    mbedtls_aead_chacha20_poly1305_context *ctx;
-    ctx = mbedtls_calloc( 1, sizeof( mbedtls_aead_chacha20_poly1305_context ) );
+    mbedtls_chachapoly_context *ctx;
+    ctx = mbedtls_calloc( 1, sizeof( mbedtls_chachapoly_context ) );
 
     if( ctx == NULL )
         return( NULL );
 
-    mbedtls_aead_chacha20_poly1305_init( ctx );
+    mbedtls_chachapoly_init( ctx );
 
     return( ctx );
 }
 
-static void aead_chacha20_poly1305_ctx_free( void *ctx )
+static void chachapoly_ctx_free( void *ctx )
 {
-    mbedtls_aead_chacha20_poly1305_free( (mbedtls_aead_chacha20_poly1305_context *) ctx );
+    mbedtls_chachapoly_free( (mbedtls_chachapoly_context *) ctx );
     mbedtls_free( ctx );
 }
 
-static const mbedtls_cipher_base_t aead_chacha20_poly1305_base_info = {
+static const mbedtls_cipher_base_t chachapoly_base_info = {
     MBEDTLS_CIPHER_ID_CHACHA20,
     NULL,
 #if defined(MBEDTLS_CIPHER_MODE_CBC)
@@ -1404,12 +1405,12 @@
 #if defined(MBEDTLS_CIPHER_MODE_STREAM)
     NULL,
 #endif
-    aead_chacha20_poly1305_setkey_wrap,
-    aead_chacha20_poly1305_setkey_wrap,
-    aead_chacha20_poly1305_ctx_alloc,
-    aead_chacha20_poly1305_ctx_free
+    chachapoly_setkey_wrap,
+    chachapoly_setkey_wrap,
+    chachapoly_ctx_alloc,
+    chachapoly_ctx_free
 };
-static const mbedtls_cipher_info_t aead_chacha20_poly1305_info = {
+static const mbedtls_cipher_info_t chachapoly_info = {
     MBEDTLS_CIPHER_CHACHA20_POLY1305,
     MBEDTLS_MODE_NONE,
     256,
@@ -1417,9 +1418,9 @@
     12,
     0,
     64,
-    &aead_chacha20_poly1305_base_info
+    &chachapoly_base_info
 };
-#endif /* MBEDTLS_AEAD_CHACHA20_POLY1305_C */
+#endif /* MBEDTLS_CHACHAPOLY_C */
 
 #if defined(MBEDTLS_CIPHER_NULL_CIPHER)
 static int null_crypt_stream( void *ctx, size_t length,
@@ -1580,8 +1581,8 @@
     { MBEDTLS_CIPHER_CHACHA20,             &chacha20_info },
 #endif
 
-#if defined(MBEDTLS_AEAD_CHACHA20_POLY1305_C)
-    { MBEDTLS_CIPHER_CHACHA20_POLY1305,    &aead_chacha20_poly1305_info },
+#if defined(MBEDTLS_CHACHAPOLY_C)
+    { MBEDTLS_CIPHER_CHACHA20_POLY1305,    &chachapoly_info },
 #endif
 
 #if defined(MBEDTLS_CIPHER_NULL_CIPHER)