All new illustrations / diagrams

[shiffman]

i'm using this issue to keep track of any new or changed line drawings (not screenshots) that need to be created or fixed for 2nd edition:

numbering is from 150f3c272c0b23c7d776a15434f7e9ed render

• [x] 2.1 new Processing PDE window with sketched overlay
• [x] 2.5 new Processing PDE window with sketched overlay
• [x] 2.6 new Processing PDE window with sketched overlay
• [x] 4.5 circleX rethink this one? also off in current render
• [ ] OOP diagram in 8.3 writing the cookie cutter needs to be fixed, also given a figure number?
• [x] 8.6 new pass by value/ref diagram!
• [x] 18.10 -- array diagram
• [x] 18.11 -- associatve array diagram
• [x] 19.1, 19.2 -- these need to be redone perhaps combined into one?

Finally, if it's not too much of a hassle this should be fixed for all illustrations:

• [x] code style standards update

[shiffman]

8.3 covered in separate issue.