Make utmp-handling more standards-compliant.

As utmpx is standardized by POSIX, first attempt to access the utmpx
database using the standard getutxent() function. If we don't have
utmpx, fall back to some simple utmp code that accesses the database
manually.

This code has been compile-tested on FreeBSD 8 (utmp), FreeBSD 9 (utmpx)
and Ubuntu Linux 11.10 (utmpx).
fix build with XCode 4.3

- avoid use of FlatCarbon headers

- remove sysroot/syslibroot

- fix gemspec files attribute
fix gemspec files filter
Fix building java bindings on Mac OSX 10.8

* look for SDKs in their new location inside the
  application bundle of XCode
Merge pull request #11 from EdSchouten/master

Make utmp-handling more standards-compliant.
Merge pull request #24 from ville-k/master

OSX 10.8 - fix building java bindings
Merge remote-tracking branch 'source/master'