Negative diameter circle turtle support

[RedGl0w]

This patch #1506

[NumWorksBot]

	.text	.rodata	.bss	.data
Base	640 932 bytes	231 699 bytes	174 952 bytes	208 bytes
Head	640 964 bytes	231 699 bytes	174 952 bytes	208 bytes
	+ 32 bytes	+ 0 bytes	+ 0 bytes	+ 0 bytes
	+ 0 %	+ 0 %	+ 0 %	+ 0 %

[artaxxx]

Thanks @RedGl0w ! It works great!

[Ecco]

One quick remark : aren't we re-inventing fabs() here? We were already using the same construct though.

[RedGl0w]

Sorry misscliclk :/

[NumWorksBot]

	.text	.rodata	.bss	.data
Base	640 932 bytes	231 699 bytes	174 952 bytes	208 bytes
Head	640 964 bytes	231 699 bytes	174 952 bytes	208 bytes
	+ 32 bytes	+ 0 bytes	+ 0 bytes	+ 0 bytes
	+ 0 %	+ 0 %	+ 0 %	+ 0 %

[RedGl0w]

One quick remark : aren't we re-inventing fabs() here? We were already using the same construct though.

If you are talking of

(radius > 0 ? 1 : -1)

This was already used in the same line, so I thought the same it was, the better it was... If you prefer a cleaner solution, I can change the whole line 😄