Blender Git Loki

Bug 1136

Saving images from UV editing window was confused... initially I thought
it only used the same format as input image, but it did use the same
as F10 buttons specified, sorta. Fixes include:

- BIF_write_ibuf() now uses current Scene renderdata to check for
image type (it checked the global R struct instead, which is only
set correct after render)
- Fileselector now gives correct title in bar (like "SAVE TARGA")
- Pulldown menu in UV window now always gives the "Save" option
- removed the weird usage of BTST() to check for flags, and made it
using the #defines instead for readability