In the situation where the amount of content preceeding the hunk was
greater than the max context of the hunk there would be an unsigned
underflow, as the logic was assuming signed arithmitic.
This underflow would result in the patch not applying, as patch would
assume the massive calculated fuzz would result in the patch matching
against any file.
We should still add an informational message about when this happens
before we even get here - but we still shouldn't be able to locate a
place to apply a hunk as it ends up producing unexpected results where
the patch is prepended to the existing file.
Given a set of lines from the file we are patching, and a patch itself,
this function will try and locate where in the file to apply that patch,
and write the result of patching that file (if successful) to the output
stream.
