Changed naming and prototype convention for x509write functions

CSR writing functions now start with x509write_csr_*()
DER writing functions now have the context at the start instead of the
end conforming to other modules.
diff --git a/tests/suites/test_suite_x509write.data b/tests/suites/test_suite_x509write.data
index c498436..7a48440 100644
--- a/tests/suites/test_suite_x509write.data
+++ b/tests/suites/test_suite_x509write.data
@@ -1,27 +1,27 @@
 Certificate Request check Server1 SHA1
 depends_on:POLARSSL_SHA1_C
-x509_cert_req_check:"data_files/server1.key":POLARSSL_MD_SHA1:"data_files/server1.req.sha1"
+x509_csr_check:"data_files/server1.key":POLARSSL_MD_SHA1:"data_files/server1.req.sha1"
 
 Certificate Request check Server1 SHA224
 depends_on:POLARSSL_SHA256_C
-x509_cert_req_check:"data_files/server1.key":POLARSSL_MD_SHA224:"data_files/server1.req.sha224"
+x509_csr_check:"data_files/server1.key":POLARSSL_MD_SHA224:"data_files/server1.req.sha224"
 
 Certificate Request check Server1 SHA256
 depends_on:POLARSSL_SHA256_C
-x509_cert_req_check:"data_files/server1.key":POLARSSL_MD_SHA256:"data_files/server1.req.sha256"
+x509_csr_check:"data_files/server1.key":POLARSSL_MD_SHA256:"data_files/server1.req.sha256"
 
 Certificate Request check Server1 SHA384
 depends_on:POLARSSL_SHA512_C
-x509_cert_req_check:"data_files/server1.key":POLARSSL_MD_SHA384:"data_files/server1.req.sha384"
+x509_csr_check:"data_files/server1.key":POLARSSL_MD_SHA384:"data_files/server1.req.sha384"
 
 Certificate Request check Server1 SHA512
 depends_on:POLARSSL_SHA512_C
-x509_cert_req_check:"data_files/server1.key":POLARSSL_MD_SHA512:"data_files/server1.req.sha512"
+x509_csr_check:"data_files/server1.key":POLARSSL_MD_SHA512:"data_files/server1.req.sha512"
 
 Certificate Request check Server1 MD4
 depends_on:POLARSSL_MD4_C
-x509_cert_req_check:"data_files/server1.key":POLARSSL_MD_MD4:"data_files/server1.req.md4"
+x509_csr_check:"data_files/server1.key":POLARSSL_MD_MD4:"data_files/server1.req.md4"
 
 Certificate Request check Server1 MD5
 depends_on:POLARSSL_MD5_C
-x509_cert_req_check:"data_files/server1.key":POLARSSL_MD_MD5:"data_files/server1.req.md5"
+x509_csr_check:"data_files/server1.key":POLARSSL_MD_MD5:"data_files/server1.req.md5"