Update parse-pbf.c for protobuf 1.0.X

Update parse-pbf.c replacing "protobuf_c_default_allocator" with "NULL" so that it compiles with protobuf 1.0.1.
Merge pull request #25 from alex85k/from-master

Use "Update parse-pbf.c for protobuf 1.0.X" commit from master branch