[gomp] Add thread attribute customization

[gomp] Add thread attribute customization

libgomp/ChangeLog

	* config/posix/pool.h (gomp_adjust_thread_attr): New.
	* config/rtems/pool.h (gomp_adjust_thread_attr): Likewise.
	(gomp_thread_pool_reservoir): Add priority member.
	* confi/rtems/proc.c (allocate_thread_pool_reservoir): Add
	priority.
	(parse_thread_pools): Likewise.
	* team.c (gomp_team_start): Call configuration provided
	gomp_adjust_thread_attr(). Destroy thread attributes if
	necessary.
	* libgomp.texi: Document GOMP_RTEMS_THREAD_POOLS.

From-SVN: r227442