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().

libasn1compiler/asn1c_C.c

@@ -2409,7 +2409,7 @@ emit_default_string_value(arg_t *arg, asn1p_value_t *v) {
 		uint8_t *e = v->value.string.size + b;
 		OUT("{ ");
 		for(;b < e; b++)
-			OUT("0x%02x, ", *b);
+			OUT("0x%02X, ", *b);
 		OUT("0 };\n");
 	}
 }
@@ -2422,7 +2422,7 @@ emit_default_bitstring_value(arg_t *arg, asn1p_value_t *v) {
 
 	uint8_t *b = v->value.binary_vector.bits;
 	for (int i = 0; i < (v->value.binary_vector.size_in_bits + 7)/8; i++, b++) {
-		OUT("0x%02x", *b);
+		OUT("0x%02X", *b);
 		if(i < (v->value.binary_vector.size_in_bits + 7)/8 - 1)
 			OUT(", ");
 	}