Move get_section implementation from dwarf::impl to dwarf
Move get_section implementation from dwarf::impl to dwarf

Since dwarf::impl is no longer used outside of class dwarf, this
function no longer has to live in both dwarf and dwarf::impl.

aclements/libelfin,tempbottle/libelfin,abenkhadra/libelfin,abenkhadra/libelfin,aclements/libelfin,abenkhadra/libelfin,abenkhadra/libelfin,tempbottle/libelfin,aclements/libelfin,aclements/libelfin