gmod_src: Added HTML:IsLoading()

Revision 876
Added HTML:IsLoading()
HTML has a callback PageTitleChanged( newtitle )
HTML has a new member .PageTitle Changed Files:
[ul]
[li]trunk/src_garrysmod/garrysmod/Objects/cl_lua_panel.cpp [/li][li]trunk/src_garrysmod/public/vgui_controls/HTML.h [/li][li]trunk/src_garrysmod/vgui2/vgui_controls/HTML.cpp[/li][/ul]

Committed By Garry Newman