MAINT-1891: FIX Updating the LLPipeline::clearRebuildGroups() to preserve HUD groups.  clearRebuildGroups() is called during the teleport process.  In the previous state, HUD objects were being incorrectly removed from the rebuild groups during the teleport process.  This change will preserve HUD groups and should resolve this issue.

MAINT-1890: A hacky fix for flexi-prim updates after teleport by ignoring the sUpdateDelay value and simply updating all flexi-prims.  This change most likely reduces frame rate.

* Improve draw performance of scroll lists by only drawing what is visible
* Reduce frequency of expensive column width calculations
Fixes by Richard

* Remove debug spam

MAINT-1894: FIX This *should* fix a crash in the LLVolume::resizePath() method.  The callstacks indicated that the std library was throwing a length exception on the std::vector::resize() call.  Most likely cause was that the recent changes for flexi-prims were causing the mRenderRes to become negative.  And thus, the 1<<mRenderRes calculation was generating a really large value for num_render_sections.

* LLScrollListControl to use LLAvatarNameCache instead of gCacheName

* Use LLAvatarNameCache in group UI to match what namelists use and prevent double lookups
* Remove LLSD -> Prams legacy pattern which is super slow.
* Member list on general tab only adds to the list after names are known

* Fix bad font name in llpanelgrouplandmoney

* llpanelgroupinvite to use LLAvatarNameCache isntead of legacy gCacheName

* Clean up 'is group' extra data in namelists.

* Split avatar name requests up among multiple frames to prevent overloading
  the nameserver and having requests time out.

MAINT-1228, MAINT-1668:  Deleting code that had been originally deleted to fix these issues, but then was accidentally re-introduced during a bad merge.