multi-threaded paging, where the Pager manages threads of reading local
and http files via seperate threads. This makes it possible to smoothly
browse large databases where parts of the data are locally cached while
others are on a remote server. Previously with this type of dataset
the pager would stall all paging while http requests were being served,
even when parts of the models are still loadable virtue of being in the
local cache.
Also as part of the refactoring the DatabaseRequest are now stored in the
ProxyNode/PagedLOD nodes to facilitate quite updating in the cull traversal,
with the new code avoiding mutex locks and searches. Previous on big
databases the overhead involved in make database requests could accumulate
to a point where it'd cause the cull traversal to break frame. The overhead
now is negligable.
Finally OSG_FILE_CACHE support has been moved from the curl plugin into
the DatabasePager. Eventually this functionality will be moved out into
osgDB for more general usage.
ReaderWriter::ReadResult now has a FILE_REQUEST enum.
ReaderWriter::Options now has a s/getAsynchronousFileReadHint() parameter methods.
libcurl based plugin now detects enabing of the AsynchronousFileReadHint, but
as yet does not handle async requests - handling everything syncronously.
DatabasePager now by default will enable AsynchronousFileReadHint for http
based file requests
