Accept a trailing space at end of PEM lines

With certs being copy-pasted from webmails and all, this will probably become
more and more common.

closes #226
diff --git a/tests/suites/test_suite_x509parse.data b/tests/suites/test_suite_x509parse.data
index 6ab4b21..5bd2af4 100644
--- a/tests/suites/test_suite_x509parse.data
+++ b/tests/suites/test_suite_x509parse.data
@@ -1368,3 +1368,7 @@
 X509 File parse (all certificates fail)
 depends_on:MBEDTLS_ECP_C
 x509parse_crt_file:"data_files/server7_all_space.crt":MBEDTLS_ERR_PEM_INVALID_DATA + MBEDTLS_ERR_BASE64_INVALID_CHARACTER
+
+X509 File parse (trailing spaces, OK)
+depends_on:MBEDTLS_ECP_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED
+x509parse_crt_file:"data_files/server7_trailing_space.crt":0