Fixed the above, including malformed bitstrings and set/sequences. Except:

Need decision on decode(bad INTEGER/BOOLEAN) and encode(bad tag):

• decode.c is quite lax about what it accepts. Should we tighten that when feasible, or remain "liberal in what we accept"?

  E.g. it accepts BER INTEGER length 0 and BOOLEAN length != 1, and wrong CONSTRUCTED/PRIMITIVE encoding bit.

• encode.c willingly stores broken identifier octets if passed an invalid tag, e.g. a single octet with low bits 0x1F implying long tag format. I'm inclined to leave that alone, caller's responsibility.

API matters:

I'll export the new function ber_peek_element(). And if nobody disagrees, the matching function ber_skip_element() even though that is nearly a duplicate of ber_get_stringbv(,, LBER_BV_NOTERM).