Do not access uninitialized memory in getink.

[lambdafu]

The getink code is a bloodbath, but more importantly, it accesses invalid memory in certain code paths:

File Edit Options Buffers Tools Help                                                                                                                                           
_imaging.c: In function ‘getink’:
_imaging.c:474:9: warning: ‘r’ may be used uninitialized in this function [-Wmaybe-uninitialized]
     int r, g, b, a;
              ^

Valgrind complains:

[Pillow]$ PYTHONPATH=. valgrind python Tests/test_image.py
==23998== Conditional jump or move depends on uninitialised value(s)
==23998==    at 0x11C0FB0D: getink (_imaging.c:495)
==23998==    by 0x11C1054C: _draw_ink (_imaging.c:2375)
==23998==    by 0x4F178BD: PyEval_EvalFrameEx (in /usr/lib64/libpython2.7.so.1.0)
==23998==    by 0x4F186B3: PyEval_EvalCodeEx (in /usr/lib64/libpython2.7.so.1.0)
==23998==    by 0x4F175C5: PyEval_EvalFrameEx (in /usr/lib64/libpython2.7.so.1.0)
==23998==    by 0x4F186B3: PyEval_EvalCodeEx (in /usr/lib64/libpython2.7.so.1.0)
==23998==    by 0x4F175C5: PyEval_EvalFrameEx (in /usr/lib64/libpython2.7.so.1.0)
==23998==    by 0x4F17665: PyEval_EvalFrameEx (in /usr/lib64/libpython2.7.so.1.0)
==23998==    by 0x4F186B3: PyEval_EvalCodeEx (in /usr/lib64/libpython2.7.so.1.0)
==23998==    by 0x4EA45AB: ??? (in /usr/lib64/libpython2.7.so.1.0)
==23998==    by 0x4E7FB02: PyObject_Call (in /usr/lib64/libpython2.7.so.1.0)
==23998==    by 0x4E8E95B: ??? (in /usr/lib64/libpython2.7.so.1.0)

The patch fixes it and removes some redundancies. I stopped short of rewriting the whole function (but I am not saying it would be a bad idea :).

[wiredfool]

See also #1663, which is also stuck on failing in appveyor.

[lambdafu]

I'm fine with closing this, #1663 covers it well. Sorry, I didn't check too closely the existing reports.

[wiredfool]

No worries. I'll take a look and see how our patches compare. Unfortunately, they appear to be both failing on windows, which is why the other one is stalled.

[wiredfool]

I've found the bug on windows in the other PR, and it looks to be more complete, so closing this one in favor of #1663.