perf annotate: add support to add samples to all symbols up the callchain

symbol__inc_addr_samples_cumulate walkes the callchain up and adds a hit
in the histogram of the calling function at the calling address.

symbol__inc_addr_samples_cumulate can be called instead of
symbol__inc_addr_samples
perf annotate: add --cumulate option

If this option is set, sampling hits are added to every function in the
callchain of the sample.
It requires callchain information, thus the use_callchain option will be
set if cumulate_callchain option is set.
perf annotate: add support for --cumulate option in perf_evsel__add_sample

In perf_evsel__add_sample, callchain informations are beeing handled if
cumulate_callchain option is set.
perf annotate: fixed two segfaults caused by NULL function pointers

Don't know if this is the right solution, but it fixes the segfaults.