common/config.h: declaration of config_option as struct

Change declaration of config_option from 'class' to 'struct' since
it's defined as struct and used this way (access members). The declaration
as class doesn't change the behaviour.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
src/msg/msg_types.h: pass function parameter by reference

Fix "Function parameter 'm' should be passed by reference." from cppchecker.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
common/AsyncReserver.h: use empty() instead of size()

Fix warning for usage of queue.size() in do_queues(). Use empty()
since it should be prefered as it has, following the standard, a
constant time complexity regardless of the containter type. The
same is not guaranteed for size().

warning from cppchecker was:
[common/AsyncReserver.h:40]: (performance) Possible inefficient
  checking for 'queue' emptiness.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
common/WorkQueue.h: use empty() instead of size()

Fix warning for usage of out->size() in _void_dequeue(). Use empty()
since it should be prefered as it has, following the standard, a
constant time complexity regardless of the containter type. The
same is not guaranteed for size().

warning from cppchecker was:
[common/WorkQueue.h:97]: (performance) Possible inefficient
  checking for 'queue' emptiness.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
src/log/Entry.h: pass function parameter by reference

Fix "(performance) Function parameter 's' should be passed by reference."
from cppchecker.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
src/mon/PGMonitor.cc: remove unused variable

Remove unused variable to fix:

mon/PGMonitor.cc:170:11: warning: unused variable 'now'
  [-Wunused-variable]

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
src/msg/Messenger.h: pass function parameter by reference

Fix "(performance) Function parameter 'm' should be passed by reference."
from cppchecker.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
src/osd/OSD.h: use empty() instead of size()

Fix warning for usage of *.size(). Use empty() since it should be
prefered as it has, following the standard, a constant time
complexity regardless of the containter type. The same is not
guaranteed for size().

warning from cppchecker was:
[osd/OSD.h:265]: (performance) Possible inefficient checking for
   'last_scrub_pg' emptiness.
[osd/OSD.h:274]: (performance) Possible inefficient checking for
   'last_scrub_pg' emptiness.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
src/osd/PG.h: use empty() instead of size()

Fix warning for usage of objects.size(). Use empty() since it
should be prefered as it has, following the standard, a constant
time complexity regardless of the containter type. The same is not
guaranteed for size().

warning from cppchecker was:
[osd/PG.h:599]: (performance) Possible inefficient checking for
  'objects' emptiness.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
test_mon_workloadgen.cc: fix -Wgnu

Fix warning from clang(++):

 test/mon/test_mon_workloadgen.cc:311:23: warning: in-class
 initializer for static data member of type 'const double' is
 a GNU extension [-Wgnu]

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
librados/librados.cc: fix implicitly-defined namespace 'std'

Fix warning from clang(++):

librados/librados.cc:15:17: warning: using directive refers to
 implicitly-defined namespace 'std'
using namespace std;
                ^
Include what we need and use the related classes.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
ceph_authtool.cc: fix implicitly-defined namespace 'std'

Fix warning from clang(++):

ceph_authtool.cc:15:17: warning: using directive refers to
 implicitly-defined namespace 'std'
using namespace std;
                ^
Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
Mutex.cc: fix implicitly-defined namespace 'std'

Fix warning from clang(++):

common/Mutex.cc:14:17: warning: using directive refers to
  implicitly-defined namespace 'std'
using namespace std;
                ^

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
Merge pull request #47 from dalgaaf/wip-da-sca-cppcheck-clang-2

fix more issues from clang(++) and cppchecker

Reviewed-by: Sage Weil <sage@inktank.com>