Add few compiler warning flags to error

[christophfroehlich]

Similar to ros-controls/ros2_controllers#961

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 18.18182% with 9 lines in your changes missing coverage. Please review.

Project coverage is 51.20%. Comparing base (795b9e6) to head (9f54dec).

Files with missing lines	Patch %	Lines
src/limited_proxy.cpp	0.00%	9 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##           ros2-master     #219   +/-   ##
============================================
  Coverage        51.20%   51.20%           
============================================
  Files               10       10           
  Lines              496      496           
  Branches            59       59           
============================================
  Hits               254      254           
  Misses             215      215           
  Partials            27       27           

Flag	Coverage Δ
unittests	51.20% <18.18%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/pid.cpp	92.64% <100.00%> (ø)
src/limited_proxy.cpp	0.00% <0.00%> (ø)

[saikishor]

LGTM