Nil is defined as NULL on OSX.
OSX: Support macports glibtoolize.
OSX: Didn't find headers if already installed.
Merge pull request #28 from Socapex/master

Various small fixes for OS X.
configure: provide options to skip utils
move demoSSL into utils
Merge pull request #27 from tmatth/autoconf

configure: provide options to skip tests/utils
updated for next release
uptick abi version
since new abi, some chance for cleanup too
more const cleanup, thread syncs mutable
use mutable autolocks/depreciate lock/unlock
updated for windows
mutable crits
improved protection macros