multiple window groups
Merge branch 'david-V08' of /Docs/fpc/fpgui into david-group-windows
fpg_tree: create a node with its tree passed as param
merged changes from David
merged in David changes along with local treeview changes
detect infinite loops in tree nodes
merge from Graeme/David
note runtime error in agg_pixfmt_bitbuf (running AB commit b082db2ea834c2549e6724f442dd11aad0ad3e31 and selecting graphics. sarala commit 4c83ecff02e8df42bfcdbcd2f930276e3dd1982f)
agg_pixfmt_bitbuf: fix focus_bit bug introduced in 1611603c0032f0d105245f51fe62a1480175cbd1, causing crashes. Also add unit to fpgui laz package.