Add conditions on VxWorks versions for gcc.dg/vxworks/initpri?.c

Adjust vxworks initpri expectations, given that vxworks7 has switched
to .init_array.


for  gcc/testsuite/ChangeLog

	* gcc.dg/vxworks/initpri1.c: Tigthen VxWorks version check.
	* gcc.dg/vxworks/initpri2.c: Likewise.