Solely use raw X.509 name data references including SEQUENCE header

So far, the CRT frame structure `mbedtls_x509_crt_frame` used
as `issuer_raw` and `subject_raw` the _content_ of the ASN.1
name structure for issuer resp. subject. This was in contrast
to the fields `issuer_raw` and `subject_raw` from the legacy
`mbedtls_x509_crt` structure, and caused some information
duplication by having both variants `xxx_no_hdr` and `xxx_with_hdr`
in `mbedtls_x509_crt` and `mbedtls_x509_crt_frame`.

This commit removes this mismatch by solely using the legacy
form of `issuer_raw` and `subject_raw`, i.e. those _including_
the ASN.1 name header.
diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index f00e44b..6757e2a 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -3001,7 +3001,7 @@
             if( ret != 0 )
                 return( ret );
 
-            dn_size = frame->subject_raw_with_hdr.len;
+            dn_size = frame->subject_raw.len;
 
             if( end < p ||
                 (size_t)( end - p ) < dn_size ||
@@ -3014,7 +3014,7 @@
 
             *p++ = (unsigned char)( dn_size >> 8 );
             *p++ = (unsigned char)( dn_size      );
-            memcpy( p, frame->subject_raw_with_hdr.p, dn_size );
+            memcpy( p, frame->subject_raw.p, dn_size );
             p += dn_size;
 
             MBEDTLS_SSL_DEBUG_BUF( 3, "requested DN", p - dn_size, dn_size );