Fix issue 293 by handling default value with type ATV_BITVECTOR
Fix issue 293 by handling default value with type ATV_BITVECTOR

1. Modify asn1p_y.c and asn1p_y.y to fix an error that
   function _convert_bitstring2binary() always return NULL.

2. Add handling for default value with type ATV_BITVECTOR in
   function try_inline_default().

mouse07410/asn1c,mouse07410/asn1c,mouse07410/asn1c,mouse07410/asn1c