Fortran: Fix memory leak in finalization wrappers [PR68800]

Fortran: Fix memory leak in finalization wrappers [PR68800]

If a finalization is not required we created a namespace containing
formal arguments for an internal interface definition but never used
any of these. So the whole sub_ns namespace was not wired up to the
program and consequently was never freed. The fix is to simply not
generate any finalization wrappers if we know that it will be unused.
Note that this reverts back to the original r190869
(8a96d64282ac534cb597f446f02ac5d0b13249cc) handling for this case
by reverting this specific part of r194075
(f1ee56b4be7cc3892e6ccc75d73033c129098e87) for PR fortran/37336.

valgrind summary for e.g.
gfortran.dg/abstract_type_3.f03 and gfortran.dg/abstract_type_4.f03
where ".orig" is pristine trunk and ".mine" contains this fix:

at3.orig.vg:LEAK SUMMARY:
at3.orig.vg-   definitely lost: 8,460 bytes in 11 blocks
at3.orig.vg-   indirectly lost: 13,288 bytes in 55 blocks
at3.orig.vg-     possibly lost: 0 bytes in 0 blocks
at3.orig.vg-   still reachable: 572,278 bytes in 2,142 blocks
at3.orig.vg-        suppressed: 0 bytes in 0 blocks
at3.orig.vg-
at3.orig.vg-Use --track-origins=yes to see where uninitialised values come from
at3.orig.vg-ERROR SUMMARY: 38 errors from 33 contexts (suppressed: 0 from 0)
--
at3.mine.vg:LEAK SUMMARY:
at3.mine.vg-   definitely lost: 344 bytes in 1 blocks
at3.mine.vg-   indirectly lost: 7,192 bytes in 18 blocks
at3.mine.vg-     possibly lost: 0 bytes in 0 blocks
at3.mine.vg-   still reachable: 572,278 bytes in 2,142 blocks
at3.mine.vg-        suppressed: 0 bytes in 0 blocks
at3.mine.vg-
at3.mine.vg-ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)
at3.mine.vg-ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)
at4.orig.vg:LEAK SUMMARY:
at4.orig.vg-   definitely lost: 13,751 bytes in 12 blocks
at4.orig.vg-   indirectly lost: 11,976 bytes in 60 blocks
at4.orig.vg-     possibly lost: 0 bytes in 0 blocks
at4.orig.vg-   still reachable: 572,278 bytes in 2,142 blocks
at4.orig.vg-        suppressed: 0 bytes in 0 blocks
at4.orig.vg-
at4.orig.vg-Use --track-origins=yes to see where uninitialised values come from
at4.orig.vg-ERROR SUMMARY: 18 errors from 16 contexts (suppressed: 0 from 0)
--
at4.mine.vg:LEAK SUMMARY:
at4.mine.vg-   definitely lost: 3,008 bytes in 3 blocks
at4.mine.vg-   indirectly lost: 4,056 bytes in 11 blocks
at4.mine.vg-     possibly lost: 0 bytes in 0 blocks
at4.mine.vg-   still reachable: 572,278 bytes in 2,142 blocks
at4.mine.vg-        suppressed: 0 bytes in 0 blocks
at4.mine.vg-
at4.mine.vg-ERROR SUMMARY: 3 errors from 3 contexts (suppressed: 0 from 0)
at4.mine.vg-ERROR SUMMARY: 3 errors from 3 contexts (suppressed: 0 from 0)

gcc/fortran/ChangeLog:

2018-10-12  Bernhard Reutner-Fischer  <aldot@gcc.gnu.org>

	PR fortran/68800
	* class.c (generate_finalization_wrapper): Do not leak
	finalization wrappers if they will not be used.
	* expr.c (gfc_free_actual_arglist): Formatting fix.
	* gfortran.h (gfc_free_symbol): Pass argument by reference.
	(gfc_release_symbol): Likewise.
	(gfc_free_namespace): Likewise.
	* symbol.c (gfc_release_symbol): Adjust acordingly.
	(free_components): Set procedure pointer components
	of derived types to NULL after freeing.
	(free_tb_tree): Likewise.
	(gfc_free_symbol): Set sym to NULL after freeing.
	(gfc_free_namespace): Set namespace to NULL after freeing.