Applied as 3673

Applied as 3246

Applied (morally) as 2952

Applied as 3238

Applied (mostly) as 3230

Applied (mostly) as 3225

with fixes and finishing touches by AW.

text along path

Implement a decorator curvedtext for setting text along a given path.
curvedtext switches to singlecharmode, but only while it is needed.

The basic idea has been discussed on the list and goes back to the PyX
grand masters.

Signed-off-by: Michael J Gruber <[email protected]>

Applied as r3204

Applied as r3205

Applied (mostly) as r3203 and r3201

with an early open and passing of the fd instead