Make use of internal iospawn flags more flexible.
* src/priv-io.h (IOSPAWN_FLAG_DETACHED): New. Renumber the others. * src/w32-io.c (_gpgme_io_spawn): Use DETACHED_PROCESS process only if IOSPAWN_FLAG_DETACHED is given. * src/w32-qt-io.cpp (_gpgme_io_spawn): Ditto. * src/w32-glib-io.c (_gpgme_io_spawn): Ditto. * src/assuan-support.c (my_spawn): Pass IOSPAWN_FLAG_DETACHED flags. * src/dirinfo.c (read_gpgconf_dirs): Ditto. * src/engine-gpg.c (start): Ditto. * src/engine-gpgconf.c (gpgconf_read, gpgconf_write): Ditto. * src/version.c (_gpgme_get_program_version): Ditto.