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/tests/CMakeLists.txt b/tests/CMakeLists.txt
index c7d9fad..9630538 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -44,7 +44,6 @@
     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} /WX-")
 endif(MSVC)
 
-add_test_suite(aead_chacha20_poly1305)
 add_test_suite(aes aes.ecb)
 add_test_suite(aes aes.cbc)
 add_test_suite(aes aes.cfb)
@@ -56,13 +55,14 @@
 add_test_suite(camellia)
 add_test_suite(ccm)
 add_test_suite(chacha20)
-add_test_suite(cipher cipher.aead_chacha20_poly1305)
+add_test_suite(chachapoly)
 add_test_suite(cipher cipher.aes)
 add_test_suite(cipher cipher.arc4)
 add_test_suite(cipher cipher.blowfish)
 add_test_suite(cipher cipher.camellia)
 add_test_suite(cipher cipher.ccm)
 add_test_suite(cipher cipher.chacha20)
+add_test_suite(cipher cipher.chachapoly)
 add_test_suite(cipher cipher.des)
 add_test_suite(cipher cipher.gcm)
 add_test_suite(cipher cipher.null)