lstat(2) the fd before we alloc an stl_object

This prevents calloc'ing gigabytes when we have invalid
data.
Correct format string units
0.1.5.pre gemspec rev
USE THE RIGHT WORDS

:horse: :cake: :fire: :cop:
Merge pull request #62 from sshirokov/stat-before-alloc

lstat(2) the fd before we alloc an stl_object