gskngltexturelibraryprivate.h: Fix build on Visual Studio
From the commit message:
GskNglTextureAtlasEntry structure is used as a member in two other structures in two Gsk private headers, namely
GskNglIconData, but the build breaks on Visual Studio since
GskNglTextureAtlasEntry contains a last member that is a zero-sized array that is normally OK if it is the last member of structure -or- if the structure that contains a
GskNglTextureAtlasEntry structure as its last member. Otherwise, a GCCism is involved here.
Fix the build on Visual Studio compilers by not using a zero-sized array as a last member of
GskNglTextureAtlasEntry, on Visual Studio compilers.
I understand that this will mean a bit of more memory use on Visual Studio builds.
As an alternative, please let me know if it is preferable to switch the order of the members of the
GskNglIconData structures instead--I did not do that because I am not sure things will work as intended, especially on other platforms.
For both approaches, it seems to me the gsk/OpenGL tests ran fine on the Visual Studio 2015 x64 builds
With blessings, thank you!