Merge branch 'ab/streaming-simplify'

Code clean-up. * ab/streaming-simplify: streaming.c: move {open,close,read} from vtable to "struct git_istream" streaming.c: stop passing around "object_info *" to open() streaming.c: remove {open,close,read}_method_decl() macros streaming.c: remove enum/function/vtbl indirection streaming.c: avoid forward declarations