add new symbol module to search symbols in DSO (for uprobes)

This will allow to don't hardcoding addresses of functions in ktap
scripts, that use uprobes, but instead, use normal function names.

Before this patch:
$ ktap -e 'trace probe:/path/to/bin:0xDEADBEAF' # instead some real address

After this path:
$ ktap -e 'trace probe:/path/to/bin:foo'

Works also for ret probes (%return)
Requires libelf.

Have NO_LIBELF option for makefile, for cross-builds.

Signed-off-by: Azat Khuzhin <a3at.mail@gmail.com>