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/Makefile b/library/Makefile
index de4bd5c..a4c6e35 100644
--- a/library/Makefile
+++ b/library/Makefile
@@ -47,11 +47,10 @@
 DLEXT=dll
 endif
 
-OBJS_CRYPTO=	aead_chacha20_poly1305.o	\
-		aes.o		aesni.o		arc4.o		\
+OBJS_CRYPTO=	aes.o		aesni.o		arc4.o		\
 		asn1parse.o	asn1write.o	base64.o	\
 		bignum.o	blowfish.o	camellia.o	\
-		ccm.o		chacha20.o			\
+		ccm.o		chacha20.o	chachapoly.o	\
 		cipher.o	cipher_wrap.o			\
 		cmac.o		ctr_drbg.o	des.o		\
 		dhm.o		ecdh.o		ecdsa.o		\