bug: fixes memo that didn't always display horizontal scrollbar
Grid: now developers have access to visible width/height.

Handy for adjusting column widths.
grid: now has a new OnHeaderClick event
grid demo: fixes index out of bounds error when deleting rows.

We never checked to see if there are any rows to delete.
grid demo: adds OnHeaderClick event handler test

- also updated project file settings for Lazarus IDE usage.
edittest: BeginDraw/EndDraw calls were not needed.
edittest: trackbars were never disabled
edittest: define the height of ComboBox widgets to match height of Edit widgets
MessageDialog: BeginDraw/EndDraw is not needed in HandlePaint()
agg: fixes bug when attaching a Image to TAgg2d doesn't draw lines.

I forgot to setup the internal dash generator in the TAgg2d constructor.
The AggCanvas did this automatically in the Canvas.BeginDraw() call, but
using TAdd2D via the .Attach(bitmap) didn't.
agg: removed the pointless casts. The x & y params are already PDouble's
agg: Add agg_renderer_base.fill(color) method for blending a color.

This complements the clear(color) method, which copies the color.
This is a port of r82 from AGG project on SourceForge.
agg: surfaced the new Fill(color) method in TAdd2D and agg_2d
fixes compiler hint about unused variable
code formatting: fixes the camel case of a function name.
Adds a new convenience function IsLoading to TfpgWidget
docview: replace some code with convenience function to make it more readable
debug server: updates uses clause to use fpGUI's dbugmsg unit.
new unit to do font mapping/lookups for the AggPas backend.

See the description in the unit header for more details.
grid: to prevent possible index out of bounds errors.