cwebp: fix metadata output w/lossy+alpha

Change-Id: Ic96da6523fc73a7b67c68ef8a4c9d12081f8a535
gif2webp: don't use C99 %zu

this would require a PRIuS or similar macro for proper platform
compatibility (Visual Studio for instance would be variants of %lu)

Change-Id: I2b9fcb1639db024775fb47dbcf79a2240f3d98f2
Merge "gif2webp: don't use C99 %zu" into 0.4.0
update NEWS description with new general features

Change-Id: I22be12d843e84f80965dc5f2cb16ba2475ce16ad