new unit to do font mapping/lookups for the AggPas backend.

See the description in the unit header for more details.
aggcanvas: adds preliminary font support

- moved fpg_fontcache unit to corelib/render/software/
- added fpg_fontcache unit to x11 fpgui_toolkit.lpk package
- translates FontDesc to FontCache item.

Tested under X11 only.
aggcanvas: added support for font rotation

The FontDesc property now supports a new font attribute:
for example:  Arial-13:Angle=45.0

The Angle range is between 0-360
maximus: Object Pascal highlighter. improve hilight accuracy.
Agg2D: rought conversion of font point size to pixel size.

Agg2D/AggPas defines font sizes in pixels, whereas the rest of fpGUI
uses point sizes. So we needed to translate between the two. This is
just a temporary implementation. A more accurate DPI aware version will
come later.
Merge branch 'agg_fonts' into develop

Initial work on getting FontDesc to AggPas font conversion working.
So far this has only been tested under X11.