add `circle(float, float, float)` function

[rinikapaul84]

the desktop version contains circle(float, float, float) function which is an alternative to the ellipse(float, float, float, float) function when we need to draw a perfect circle. but apde doesn't.

[rar0n]

I just realized you can also add it yourself (as a work-around. But yeah would be nice to not have to do that on all sketches).

void circle(float x, float y, float s) {
   ellipse(x, y, s, s);
}

[Calsign]

circle was added to a version of Android mode that APDE has yet to update to. I am currently working on updating Android mode, and making upgrading a more streamlined process in the future. In the meantime, defining circle yourself seems like an easy, although unfortunate thing to have to do.

[code-commenter]

and "exit()" function

[Muppetsg2]

and square(float, float, float)