[DynInst_API:] [dyninst/dyninst] 14b694: Add lookup by name in block_instance::callee (#875)

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  Branch: refs/heads/master
  Home:   https://github.com/dyninst/dyninst
  Commit: 14b6941fc861eba656c5210b4ebd821c88596851
      https://github.com/dyninst/dyninst/commit/14b6941fc861eba656c5210b4ebd821c88596851
  Author: Tim Haines <thaines.astro@xxxxxxxxx>
  Date:   2020-10-05 (Mon, 05 Oct 2020)

  Changed paths:
    M dyninstAPI/src/block.h
    M dyninstAPI/src/unix.C

  Log Message:
  -----------
  Add lookup by name in block_instance::callee (#875)

* Refactor callee lookup by name into separate function
* Add callee lookup by name if lookup by PLT address fails
* Code cleanup (c++11-ify)
* Get rid of fbtvector
    It's just a copy of fbt.
* Cleanup comments