move to C++14

[sergiud]

Closes #602

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 73.99103% with 58 lines in your changes missing coverage. Please review.

Project coverage is 73.85%. Comparing base (a13d03b) to head (389ae5c).
Report is 154 commits behind head on master.

Files with missing lines	Patch %	Lines
src/windows/dirent.h	33.33%	20 Missing ⚠️
src/logging.cc	84.82%	17 Missing ⚠️
src/signalhandler.cc	18.18%	9 Missing ⚠️
src/utilities.cc	63.63%	4 Missing ⚠️
src/symbolize.cc	66.66%	3 Missing ⚠️
src/vlog_is_on.cc	76.92%	3 Missing ⚠️
src/glog/logging.h.in	50.00%	1 Missing ⚠️
src/windows/port.cc	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #902      +/-   ##
==========================================
- Coverage   73.97%   73.85%   -0.13%     
==========================================
  Files          17       17              
  Lines        3282     3251      -31     
==========================================
- Hits         2428     2401      -27     
+ Misses        854      850       -4     

Files with missing lines	Coverage Δ
src/base/googleinit.h	100.00% <ø> (ø)
src/base/mutex.h	100.00% <100.00%> (ø)
src/demangle.cc	97.47% <100.00%> (-0.02%)	⬇️
src/glog/stl_logging.h.in	100.00% <100.00%> (ø)
src/raw_logging.cc	100.00% <ø> (ø)
src/stacktrace_unwind-inl.h	92.59% <100.00%> (ø)
src/utilities.h	100.00% <100.00%> (ø)
src/windows/port.h	100.00% <100.00%> (ø)
src/glog/logging.h.in	80.28% <50.00%> (+0.28%)	⬆️
src/windows/port.cc	54.54% <80.00%> (ø)
... and 6 more