Fixed a bug where 6L38 games fail to convert packed text to unpacked text.

The conversion function introduced in 6L38, TEXT_TY_CastPrimitive in Text.i6t,
makes direct Glk calls to open a memory stream instead of calling
Glulx_PrintAnyToArray. We replace it with a version that uses
OpenOutputBufferUnicode under FyreVM.
Merge pull request #4 from taradinoc/master

Fixed a bug where 6L38 games fail to convert packed text to unpacked text.