Added 'Haiku' and 'Solaris' to 'system'.

[Cyrodwd]

A very small change. Solaris was not being used in version checking, so decided to add it. Same with HaikuOS, only there I had to add it to the OS enum manually.

To start with something small contributing to Phobos.

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[ibuclaw]

Given that haiku is not supported except on ancient compilers, and not without third party patches either (gcc2.95), should it really be considered here?

[Cyrodwd]

You have a good point, I don't know if you want to remove it in that case.