We're not formally using C++11 yet so those trigger compilation warnings
(at least with GCC 5):
./main/input_default.h:122:30: warning: non-static data member initializers only available with -std=c++11 or -std=gnu++11
CursorShape default_shape = CURSOR_ARROW;
^
Note: We may allow those eventually (especially for non-int static const),
but most of current occurrences were inconsistent with all other classes.
See also http://www.stroustrup.com/C++11FAQ.html#member-init