Add support for attach multiple uprobe

[Zhongy95]

In libbpf, attach multiple uprobes like:

		link->multi_link = bpf_program__attach_uprobe_multi(prog, pid, path,
								    NULL, &opts_multi);

https://github.com/libbpf/libbpf/blob/master/src/usdt.c

Or do we have other alternatives to attach uprobes to multiple addresses of different target?

[danielocfb]

I don't believe we have multi attach hooked up yet. Feel free to contribute the bindings.