[OpenACC] Consolidate 'GOACC_enter_exit_data' and its helper functions in 'libgomp...

[OpenACC] Consolidate 'GOACC_enter_exit_data' and its helper functions in 'libgomp/oacc-mem.c'

	libgomp/
	* oacc-parallel.c (find_pointer, GOACC_enter_exit_data): Move...
	* oacc-mem.c: ... here.
	(gomp_acc_insert_pointer, gomp_acc_remove_pointer): Rename to
	'goacc_insert_pointer', 'goacc_remove_pointer', and make 'static'.
	* libgomp.h (gomp_acc_insert_pointer, gomp_acc_remove_pointer):
	Remove.
	* libgomp_g.h: Update.

From-SVN: r279233