Reduce code size when mbedtls_x509_*_info() unused

Introduce MBEDTLS_X509_INFO to indicate the availability of the
mbedtls_x509_*_info() function and closely related APIs. When this is
not defined, also omit name and description from
mbedtls_oid_descriptor_t, and omit OID arrays, macros, and types that
are entirely unused. This saves several KB of code space.

Signed-off-by: Hanno Becker <hanno.becker@arm.com>
Signed-off-by: Chris Jones <christopher.jones@arm.com>
diff --git a/library/x509_crl.c b/library/x509_crl.c
index edeb39b..4c898c9 100644
--- a/library/x509_crl.c
+++ b/library/x509_crl.c
@@ -614,6 +614,7 @@
 }
 #endif /* MBEDTLS_FS_IO */
 
+#if defined(MBEDTLS_X509_INFO)
 /*
  * Return an informational string about the certificate.
  */
@@ -693,6 +694,7 @@
 
     return( (int) ( size - n ) );
 }
+#endif /* MBEDTLS_X509_INFO */
 
 /*
  * Initialize a CRL chain