WinRT: added scripts to build Release copies of SDL for all WinRT variants

These variants include:
 - Windows 8.0 for x86
 - Windows 8.0 for x64
 - Windows 8.0 for ARM
 - Windows 8.1 for x86
 - Windows 8.1 for x64
 - Windows 8.1 for ARM
 - Windows Phone 8.0 for x86 (for use with the Windows Phone emulator)
 - Windows Phone 8.0 for ARM
 - Windows Phone 8.1 for x86 (for use with the Windows Phone emulator)
 - Windows Phone 8.1 for ARM

--HG--
extra : rebase_source : 776b8a3680350369ed85c7769540211274bf204e