libbpf-tools: Add verbose option to funclatency
libbpf-tools: Add verbose option to funclatency

Support verbose mode and set custom libbpf print callback
in funclatency.

Signed-off-by: Hengqi Chen <2146682b4c3fe4aa97c809745b7d5be9e6165e06@outlook.com>

iovisor/bcc,iovisor/bcc,brendangregg/bcc,iovisor/bcc,brendangregg/bcc,brendangregg/bcc,iovisor/bcc,iovisor/bcc,brendangregg/bcc,brendangregg/bcc