RTDM: More IOCTL requests to be handled in primary mode

Xenomai 2 to 3 migration says "RTDM drivers implementing differentiated ioctl() support for both domains should serve all real-time only requests from ioctl_rt(), returning -ENOSYS for any unrecognized request, which will cause the adaptive switch to take place automatically to the ioctl_nrt() handler. The ioctl_nrt() should then implement all requests which may be valid from the regular Linux domain exclusively."

Cosmetic change : rtdm_in_rt_context instead of ipipe_root_p.

Xenomai won't merge .nrt ops delegation to rtdm task through rtpc. Moved it to rtdmnet.c.

Fixed wrong xeno_lib_ldflags, missing --posix --auto-init-solib

More hgignore

This fix a segfault in xenomai_posix example when calling pthread_setschedparam(cyclic_thread, ...) from main thread. As a side effect EL2004 becomes EL2088 - that's what IU have for testing.

More check in rtdm mmap, also use kernel memory instead of virtual memory.

Use new RTDM's mmap, not anymore a special case compared to normal linux mmap.

Fixed rtdmnet.c PFX and removed useless commented code.

rtdmnet module should follow same (un)loading rules as generic module

Added devices/rtdmnet.c, heavily based on devices/generic.c, and with similar purpose. It uses Xenomai's RTNet/RTDM socket instead of Linux socket.