Improve presentation of GNU archive file content in Project Explorer

[jld01]

When building a static library using a GNU toolchain, CDT presents the object files within the archive as child nodes within the Project Explorer view. However, there are issues with this behaviour:

• The location attributes of the object files are not correct. Attempts to manipulate an object file (eg to open the file) will therefore fail.
• Multiple object files with the same file name (different paths) are not presented.

It is possible to calculate the correct location of the object file by building the archive with the -P (use full path) option and using the build CWD to resolve relative paths. This should allow us to provide behaviour equivalent to the child nodes of executable files within Project Explorer.

[jld01]

Work is also required in the PEBinaryObject64 class to support object data lookup from archive as for ElfBinaryObject.