New particles are spawned around the particle emitter position according to a
configurabe distribution.
New functionality:
particlesystem:setAreaSpread(distributon, x, y)
distribution, x, y = particlesystem:getAreaSpread()
Where `distribution' is one of "none", "uniform", "normal".
`x' and `y' take different meaning based on the distribution:
* none: no area spread - particles spawned at emitter position.
* uniform: particle spawned at px,py in the rectangle around emitter
position ex,ey, i.e.:
ex - x < px < ex + x, ey - y < py < ey + y,
* normal: particle position drawn from a normal/gaussian distribution
with mean ex,ey and standard deviation x,y, i.e.:
px \in N(ex, x²), py \in N(ey, y²).
Add a extern vec2 love_ScreenSize to the pixel effects that will
be (re)set upon PixelEffect::loadVolatile() and is used to flip
the fragment coordinate.
Unfixes #324 because canvases can have different dimensions than
the screen.
Error reporting now resides in Graphics::newCanvas() instead of the
previous location wrap_newFramebuffer(). Changed error text for
"Error in implementation" to point to a possible fix.
vrld
Bart van Strien
rude
Bill Meltsner
vrld