* Optimized tree generation by adding a small_value field in every node.

* Optimized tree generation by adding a small_value field in every node.
  If the node contains few data they will be stored there instead of a
  malloced buffer.

* Added ability to DER decoder to decode BER encoded octet strings.

* Added test case with a pkcs-12 formatted structure to test the ability
  to parse those strings.

* Added asn1_append_value() and asn1_set_value_octet() to reduce code being copied.