remove Makefile.PL cruft
import libbson 0.6.4 source as vendored code
import vendored yajl from libbson 0.6.4
Configure platform-specific libbson headers

This uses Perl-based probes to replace configuration variables
that autoconfig would normally resolve.  This is suboptimal, but
hopefully will be sufficient for most common platforms.
Merge pull request #91 from mongodb/topic/vendor-libbson

Topic/vendor libbson