Fix typos (found by Francesco Pompò)

Manually merging as the pull requests are based on an old branch.

closes #215
closes #216
diff --git a/programs/x509/cert_req.c b/programs/x509/cert_req.c
index 0716466..59549bb 100644
--- a/programs/x509/cert_req.c
+++ b/programs/x509/cert_req.c
@@ -273,7 +273,7 @@
     /*
      * 1.0. Check the subject name for validity
      */
-    mbedtls_printf( "  . Checking subjet name..." );
+    mbedtls_printf( "  . Checking subject name..." );
     fflush( stdout );
 
     if( ( ret = mbedtls_x509write_csr_set_subject_name( &req, opt.subject_name ) ) != 0 )