Fixed an issue that was stopping LLDB from finding complete definitions for

types. What was happening was the DWARF parser was almost ignoring definitions
(DIEs with the DW_AT_declaration set to 1). It wasn't ignoring declarations
that had _some_ children. When this happened, we would treat the declaration
as a complete type. Often we would have a declaration of a type with just
some enum definitions inside and nothing else. Now we correctly ignore these
definitions, and also I added some changes to allow us to figure out what
decl context these special declarations actually point to.

llvm-svn: 124179