Compilation fixes for Solaris

Compile and run on Solaris (tested on SmartOS). The basic privsep
sandbox works. Support for creating Solaris containers is planned.

TODO:
* support options in mount. Flags like MS_NOEXEC are passed as strings.

* clean up compiler warnings

* add chroot test: requires a statically linked binary

* makefile: the "which" command does not return an error on Solaris