This adds a counter and a 'dead' flag to the data stored in the linked
list. The counter counts the number of iterators (still) pointing to an
element and the dead flag is set to indicate the element was erased when
iterators are still pointing to it. As a result, iterators are NEVER
invalidated. Of course, such elements are subsequentially skipped when
iterating over the list. Assertions protect against dereferencing an
erased iterator, but incrementing or decremention still works: it is
still well-defined what the next (non erased) element is, assuming the
element wasn't erased (yet), but would be erased delayed - or assuming
the iterator would have been incremented (decremented) in advance to
erasing the element.
Improved texture console progress bar visibility.
Shoehorned sgblacklist for server response status 499
Restored stat recording for LLViewerTextureList
Cleaned up lltexturefetch by excluding more unused code via #if
Need to test:
localassetbrowser
preview related floaters
hgfloatertexteditor
maps
media textures! Currently very hacky
web browser
alpha masks on avatars
bumpmaps
Are all sky components appearing?
LLViewerDynamicTexture (texture baking, browser, animated textures, anim previews, etc)
Snapshot related features
Customize avatar
vfs floater
UI textures in general
Texture priority issues
