Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Merged r262424-262425,265085

Add the -a option to pmcstat. This produces a full stack track on the
sampled points. See the man page for details on how this works.

Obtained from: Netflix, Inc.

Add a new option - 'a <file>' - which spits out annotated callgraphs.

'-m <file>' spits out the given stream into <file> (eg, /dev/stdout).
However, it only resolves the first symbol; it doesn't parse the entire
callgraph. If it fails to lookup then it doesn't print anything.

'-a' instead does a symbol and file:line lookup for each address in each
callgraph and will happily print the address itself with no lookup
information if it couldn't look things up.

This makes it much easier to pull out individual records from a
pmc data file and look at the callgraph information without having to
hand-decode the addresses.

Sponsored by: Netflix, Inc.