[Windows8] Fixing Compile Error on Debug (AllowUnsafeBlocks to true)

Need to AllowUnsafeBlocks on Debug Mode
The function float Convert(ushort value) - HalfTypeHelper
uses it
Merge pull request #1155 from tpastor/develop3d

[Windows8] Fixing Compile Error on Debug (AllowUnsafeBlocks to true)