V2 Add DWARF support to the rtemstoolkit and put it to use.

[Chris Johns]

Hi,

This is a wrap up patch of all the issues that have been raise. Thanks to
the excellent debugging and teamwork in finding the linking issue on Linux,
that is a really strange one to trip over.

The patches:

- Add a DWARF framework to the rtemstoolkit to access the
  source file and line given an address in an executable. This allows
  us to remove exec'ing addr2line in covoar.

- Add producer support to rtems-exe-info to list the compilers used
  to build the executables plus list the common flags and optionally
  list all the object files with the flags that are not common.

- Clean up exception handling in destructors in some places. This
  avoids a terminate if an exception is thrown in an exception
  unwind.

Changes since v1:

- Fix rld::path::path_abs() to not walk above the root directory.

- Fix a memory issue with the dwarf_srcfiles(). The libdwarf we are
  using manages all memory and does not need to have it dealloced
  while the man pages state it should be.

- Add producer support to collect and manage CU producer attributes.

- Remove libgen.h from covoar and use RLD path. I have not tested
  those changes.

I recommend anyone shipping RTEMS executables to run rtems-exe-info over
your executables and have a look. It will let you know if you are using
the same compiler in all parts as well as listing the machine flags
used to control GCC.

Chris