Fix #86: gdImageScale segfaults with most interpolation types

Code fails to propagate the interpolation type to an intermediate
temp image.  This change fixes that.
Merged in suetanvil/gd-libgd (pull request #11)

Fix #86: gdImageScale segfaults with most interpolation types
Merged libgd/gd-libgd into master
Fixed memory overrun bug in gdImageScaleTwoPass

_gdContributionsCalc would compute a window size and then adjust
the left and right positions of the window to make a window within
that size.  However, it was storing the values in the struct *before*
it made the adjustment.  This change fixes that.
Merge remote-tracking branch 'remotes/bitbucket-repo/suetanvil'