Draw target mechanism, new primitives, new graphics.hpp and al4 joy. ev.

- Added fgeal custom implementation of joystick events for the Allegro 4
adapter.
- Allegro 4: fail silently if could not create temporary bitmap.
- Added new graphics.hpp header, where the primitive drawing functions
are placed.
- Added Graphics::setDrawTarget() methods which set the current drawing
target for all Image class drawing and primitive drawing. It is a more
sophisticated way of blitting Image's.
- Clearing all newly created Image's through Image(int w, int h)
constructor.
- Changed SDL 1.2 adapter smoothing flags. Now there are 2 different
flags: FGEAL_SDL1_2_USE_SMOOTH_PRIMITIVES and
FGEAL_SDL1_2_USE_SMOOTH_ROTOZOOM.
- Fixed some ill examples of throwing AdapterException
- Using ALLEGTTF_REALSMOOTH flag for small fonts in the Allegro 4
adapter.
- Add Graphics::drawPolygon and Graphics::drawFilledPolygon functions,
with many different signatures.
- Add Graphics::drawArc, Graphics::drawCircleSector,
Graphics::drawFilledCircleSector functions.
- Add Graphics::drawRoundedRectangle and
Graphics::drawFilledRoundedRectangle functions, with many different
signatures.
- Include cmath in geometry.hpp with use math defines macros and
fallback.
- Some adapters: changed array usage with vector. Avoid copy-assignment.
- Other small fixes.