Remove dependency to nm and rather use libbfd, which is the same lib
used by nm. There is no additional depency, but cmake will fail if it
cannot find libbfd. There was no check for nm before.

Unit test still use nm to count the number of symbols. It provides a
double check on this implementation.

Before we would get:
$ ./build/tools/cgreen-runner ./build/tests/libbreadcrumb_tests.so
Running "libbreadcrumb_tests" (9 tests)...
  "Breadcrumb": 9 passes in 3ms.
Completed "libbreadcrumb_tests": 9 passes in 3ms.

$ ./build/tools/cgreen-runner ./build/tests/Makefile
/usr/bin/nm: ./build/tests/Makefile: file format not recognized
No tests found in './build/tests/Makefile'.

$ ./build/tools/cgreen-runner /usr/lib/libgit2.so
/usr/bin/nm: /usr/lib/libgit2.so: no symbols
No tests found in '/usr/lib/libgit2.so'.

After this patch we get:
$ ./build/tools/cgreen-runner ./build/tests/libbreadcrumb_tests.so
Running "libbreadcrumb_tests" (9 tests)...
  "Breadcrumb": 9 passes in 3ms.
Completed "libbreadcrumb_tests": 9 passes in 3ms.

$ ./build/tools/cgreen-runner ./build/tests/Makefile
No tests found in './build/tests/Makefile'.

$ ./build/tools/cgreen-runner /usr/lib/libgit2.so
No tests found in '/usr/lib/libgit2.so'.

Add depending on the distro used: /usr/lib/libbfd.(a|so). Headers and
libraries are provided by different package depending on the distro:
binutils, binutils-devel, sys-libs/binutils-libs, etc.

Following change to dicoverer.c, unit tests needed some rewriting.
Discoverer acceptance and unit tests were added to cmake.

This change allow dependency validation and parallel testing.

…erywhere

…erywhere

…y issue)

…ng runner...

When developing the cgreen-runner, we want to avoid using it for
running the unittests as to not end up with unit tests not running.

…calize

When reading a non-dynamic BFD object we need to use corresponding
non-dynamic version of the functions. This made the runner correctly
handle COFF/PE32+ files (.DLL's)

The difference is actually only which 'symtab_upper_bound' and
'canonicalize' you use.