* lang/cpp/src/Makefile.am, lang/qt/src/Makefile.am (AM_CPPFLAGS):
Add suggest-override and zero-as-null-pointer-constant warnings.
* lang/cpp/src/*, lang/qt/src/*: Consistenly use nullptr and override.
--
This was especially important for the headers so that downstream
users of GpgME++ or QGpgME do not get flooded by warnings if
they have these warnings enabled.
It also improves compiler errors/warnings in case of accidental
mistakes.
* lang/qt/src/multideletejob.h: Fix include, cryptobackend.h is now
called protocol.h
* lang/qt/src/multideletejob.cpp: New file.
* lang/qt/src/Makefile.am: Add multideletejob.cpp.
