ada: Adjust QNX Ada priorities to match QNX system priorities

ada: Adjust QNX Ada priorities to match QNX system priorities

The Ada priority range of the QNX runtime started from 0, differing from
the QNX system priorities range starting from 1. As this may cause
confusion, especially if used in a mixed language environment, the Ada
priority range now starts at 1.

The default priority of Ada tasks as mandated is the middle of the
priority range. On QNX this means the default priority of Ada tasks is
30. This is much higher than the default QNX priority of 10 and may
cause unexpected system interruptions when Ada tasks take a lot of CPU time.

gcc/ada/

	* libgnarl/s-osinte__qnx.adb: Adjust priority conversion function.
	* libgnat/system-qnx-arm.ads: Adjust priority range and default
	priority.