Go1.11 switched to the zlib-gnu compression format for debug sections.
Change proc and and a test in dwarf/line to support this change.
Also deletes some dead code from pkg/proc/bininfo.go that hadn't been
used in a long time.
go1.11 adds a new extended attribute to all type DIEs containing the
address of the corresponding runtime._type struct, use this attribute
to find the DIE of the concrete type of interface variables when
available.
Splits out type parsing and go-specific Type hierarchy from
x/debug/dwarf, replace x/debug/dwarf with debug/dwarf everywhere,
remove x/debug/dwarf from vendoring.
