ada: Revert conditional installation of signal handlers on VxWorks

ada: Revert conditional installation of signal handlers on VxWorks

The conditional installation resulted in a semantic change, and
although it is likely what is ultimately wanted (since HW interrupts
are being reworked on VxWorks). However it must be done in concert
with other modifications for the new formulation of HW interrupts and
not in isolation.

gcc/ada/

	* init.c [vxworks] (__gnat_install_handler): Revert to
	installing signal handlers without regard to interrupt_state.