- fix find_package for glog & gflags

[SSE4]

This pullrequest changes

fix find_package for glog and gflags libraries, which might have different names, e.g. in debug builds they are glogd and gflags_debug(or gflags_nothreads_debug).

[alalek]

This patch should go into 3.4 branch first. We will merge changes from 3.4 into master regularly (weekly/bi-weekly).

So, please:

• change "base" branch of this PR: master => 3.4 (use "Edit" button near PR title)
• rebase your commits from master onto 3.4 branch. For example:
  git rebase -i --onto upstream/3.4 upstream/master
  (check list of your commits, save and quit (Esc + "wq" + Enter)
  where upstream is configured by following this GitHub guide and fetched (git fetch upstream).
• push rebased commits into source branch of your fork (with --force option)

Note: no needs to re-open PR, apply changes "inplace".