We keep NULL in the pure C files in src/csync/std and test/csync.
We also replace Doxygen documentation referring to "NULL" to
"\c nullptr" (formatted as code).
Signed-off-by: Stephan Beyer <s-beyer@gmx.net>
This will allow us to unify data structures between csync and libsync.
Utility functions like csync_time and c_std are still compiled as C
since we won't need to be coupled with Qt in the short term.
Stephan Beyer