Missing header in SDK

[rachels]

The header file "istring.h" is missing from the Phoenix SDK.

Commenting out lines that reference it, including the "GetCachePath" function, allows projects to build, but would be nice to have all dependencies included in the SDK.

[Svetlin.Nikolov]

Ouch, thanks for that, will fix it!

[Svetlin.Nikolov]

The header will be in the Max version of the SDK since tomorrow's nightly, thanks again!

[rachels]

Great, thanks!