[Ada] Import binder globals as constant

[Ada] Import binder globals as constant

gcc/ada/

	* libgnarl/s-intman__android.adb, libgnarl/s-intman__lynxos.adb,
	libgnarl/s-intman__posix.adb, libgnarl/s-intman__qnx.adb,
	libgnarl/s-intman__solaris.adb, libgnarl/s-intman__susv3.adb,
	libgnarl/s-taprob.adb, libgnarl/s-taprop__hpux-dce.adb,
	libgnarl/s-taprop__linux.adb, libgnarl/s-taprop__mingw.adb,
	libgnarl/s-taprop__posix.adb, libgnarl/s-taprop__qnx.adb,
	libgnarl/s-taprop__solaris.adb, libgnarl/s-taprop__vxworks.adb,
	libgnarl/s-taskin.adb, libgnarl/s-tasque.adb,
	libgnarl/s-tpoben.adb, libgnat/a-calend.adb,
	libgnat/a-excach.adb, libgnat/a-except.adb, libgnat/a-tags.adb,
	libgnat/a-textio.adb, libgnat/a-witeio.adb,
	libgnat/a-ztexio.adb, libgnat/g-binenv.adb,
	libgnat/s-parame.adb, libgnat/s-parame__vxworks.adb,
	libgnat/s-stratt.adb, libgnat/s-trasym__dwarf.adb: Mark imported
	binder globals as constant.