Returning by reference leads to lifetime issues with the default
value which may go out of scope by the time it is used.
Thanks to @Ardavel for reporting this, as this causes graph_test
to fail on VS2015x64.
https://github.com/ceres-solver/ceres-solver/issues/216
Change-Id: I596481219cfbf7622d49a6511ea29193b82c8ba3
Since Ceres is moving to using GitHub for issues, and the Google
Code URL in the current copyright header will soon become invalid,
update all the headers.
Change-Id: I1fce70375d1bcf098591f07b4d8f01a5c1e0789c
For historical reasons we had a "using namespace std;" in port.h. This
is generally a bad idea. So removing it and along the way doing a bunch
of cpplint cleanup.
Change-Id: Ia125601a55ae62695e247fb0250df4c6f86c46c6