Check for extended key usage by traversing raw extension data

This commit re-implements `mbedtls_x509_crt_check_extended_key_usage()`
to not use the dynamically allocated linked list presentation of the
`ExtendedKeyUsage` but to search for the required usage by traversing
the raw ASN.1 data.
diff --git a/include/mbedtls/asn1.h b/include/mbedtls/asn1.h
index 2fb6de0..b49fe5a 100644
--- a/include/mbedtls/asn1.h
+++ b/include/mbedtls/asn1.h
@@ -131,6 +131,10 @@
         ( ( MBEDTLS_OID_SIZE(oid_str) != (oid_buf)->len ) ||                \
           memcmp( (oid_str), (oid_buf)->p, (oid_buf)->len) != 0 )
 
+#define MBEDTLS_OID_CMP_RAW(oid_str, oid_buf, oid_buf_len)                  \
+        ( ( MBEDTLS_OID_SIZE(oid_str) != (oid_buf_len) ) ||                 \
+          memcmp( (oid_str), (oid_buf), (oid_buf_len) ) != 0 )
+
 #ifdef __cplusplus
 extern "C" {
 #endif