General example changes

[bilhox]

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Hi, I took a look at all examples, and made some fixes.

aacircle.py :

• Removed the pretty weird try block and replaced it by a beautiful while loop

aliens.py :

• renamed all to all_sprite, because all is a native python function.
• removed depth argument
• added pygame.SCALED because on Windows, there is a problem with FULLSCREEN mode

chimp.py :

• removed RenderPlainbecause it's deprecated
• renamed some variables so it follows python naming convention

dropevent.py :

• renamed some variables because either it doesn't follow the python naming convention, or it is not intuitive

playmus.py :

• This is a proposition from Matiiss, switching from pygame.freetype to pygame.Font
• Revamped the code, as its structure isn't understandable for a beginner.

resizing_new.py :

• renamed a variable because it's not intuitive

scaletest.py :

• removed useless alias
• renamed some variables/functions because either it doesn't follow the python naming convention, or it is not intuitive

liquid.py :

• renamed some variables/functions because either it doesn't follow the python naming convention, or it is not intuitive
• remove time.sleep so it uses pygame.Clock

[bilhox]

This should fix #2518