No need to specify all the files in it manually.
SUBDIRS=library
-EXTRA_DIST=ChangeLog LICENSE README.rst include/polarssl/bignum.h include/polarssl/compat-1.2.h include/polarssl/blowfish.h include/polarssl/pk_wrap.h include/polarssl/md5.h include/polarssl/net.h include/polarssl/x509.h include/polarssl/aes.h include/polarssl/ctr_drbg.h include/polarssl/padlock.h include/polarssl/ssl_ciphersuites.h include/polarssl/cipher_wrap.h include/polarssl/pkcs11.h include/polarssl/asn1write.h include/polarssl/threading.h include/polarssl/md4.h include/polarssl/certs.h include/polarssl/des.h include/polarssl/bn_mul.h include/polarssl/md2.h include/polarssl/xtea.h include/polarssl/ecdh.h include/polarssl/asn1.h include/polarssl/oid.h include/polarssl/pbkdf2.h include/polarssl/debug.h include/polarssl/base64.h include/polarssl/config.h include/polarssl/havege.h include/polarssl/camellia.h include/polarssl/rsa.h include/polarssl/ecdsa.h include/polarssl/md_wrap.h include/polarssl/gcm.h include/polarssl/x509_csr.h include/polarssl/pem.h include/polarssl/entropy_poll.h include/polarssl/pkcs12.h include/polarssl/md.h include/polarssl/openssl.h include/polarssl/ecp.h include/polarssl/version.h include/polarssl/x509_crl.h include/polarssl/sha512.h include/polarssl/entropy.h include/polarssl/pk.h include/polarssl/cipher.h include/polarssl/arc4.h include/polarssl/x509_crt.h include/polarssl/ssl_cache.h include/polarssl/sha1.h include/polarssl/pkcs5.h include/polarssl/memory.h include/polarssl/dhm.h include/polarssl/timing.h include/polarssl/ssl.h include/polarssl/error.h include/polarssl/sha256.h
+EXTRA_DIST = ChangeLog LICENSE README.rst include/polarssl