Code review comment for lp:~widelands-dev/widelands/richtext_testing

After the tweaks done by Tino, most of the failures have gone away on Ubuntu too.
However the two remaining ones require a substantial increase in the difference tolerated that I worry it will end up passing things which should fail.

See the output below for details, but these are the values I found when experimenting.

kMaxClearDistance values
8 (hline + font_shadow failing)
120 (hline starts passing)
256+ Everyting passes, but I assume I have made the tests useless at this point.

Mismatched pixel: (92, 0)
 expected: (0, 0, 0, 0)
 seen: (255, 255, 255, 0)
Mismatched pixel: (48, 19)
 expected: (0, 0, 0, 0)
 seen: (255, 255, 255, 0)
Mismatched pixel: (65, 20)
 expected: (0, 0, 0, 0)
 seen: (255, 255, 255, 0)
Mismatched pixel: (0, 39)
 expected: (0, 0, 0, 0)
 seen: (255, 255, 255, 0)
 wrong pixels: 0.00 %
Render output of data/font_shadow/input00.txt does not compare equal to correct.png. Saved wrong.png.
/home/user/dev/richtext_testing/src/graphic/text/test/test_richtext_renderer.cc(261): error in "font_shadow": check compare_for_test(sar.renderer()) failed

Mismatched pixel: (0, 24)
 expected: (255, 255, 255, 1)
 seen: (203, 187, 136, 1)
Mismatched pixel: (1, 24)
 expected: (204, 204, 153, 5)
 seen: (225, 208, 146, 5)
Mismatched pixel: (198, 24)
 expected: (255, 255, 127, 2)
 seen: (225, 205, 142, 2)
Mismatched pixel: (199, 24)
 expected: (0, 0, 0, 1)
 seen: (112, 58, 3, 1)
Mismatched pixel: (0, 25)
 expected: (204, 204, 153, 5)
 seen: (215, 196, 135, 5)
Mismatched pixel: (199, 25)
 expected: (170, 85, 0, 3)
 seen: (152, 88, 3, 3)
 wrong pixels: 0.00 %
Render output of data/hline/input00.txt does not compare equal to correct.png. Saved wrong.png.
/home/user/dev/richtext_testing/src/graphic/text/test/test_richtext_renderer.cc(266): error in "hline": check compare_for_test(sar.renderer()) failed