Add dladdr to libroot

[romain]

Revision 27972

The enclosed patch adds "dladdr". function. dladdr is a gnu extension to the "dl*" posix apis.

I tried to respect coding guidelines, but it may not be fully compliant.

The enclosed patch is not thread safe due to the 2 static variables. However I did not find another solution to fill the Dl_info structure without this. The only other way I see would require modifications in the runtime loader so that we get pointer to the elf object himself, and not copies.

Implementation is heavily inspired from the netbsd one.

[romain]

Patch update based on axel's remarks

[axeld]

Thanks for the update! Applied in r28308.