fortran: Undo new symbols in all namespaces [PR110996]

fortran: Undo new symbols in all namespaces [PR110996]

Remove new symbols from all namespaces they may have been added to in case a
statement mismatches in the end and all the symbols referenced in it have to
be reverted.

This fixes memory errors and random internal compiler errors caused by
a new symbol left with dangling pointers but not properly removed from the
namespace at statement rejection.

Before this change, new symbols were removed from their own namespace
(their ns field) only.  This change additionally removes them from the
namespaces pointed to by respectively the gfc_current_ns global variable,
and the symbols' formal_ns field.

	PR fortran/110996

gcc/fortran/ChangeLog:

	* gfortran.h (gfc_release_symbol): Set return type to bool.
	* symbol.cc (gfc_release_symbol): Ditto.  Return whether symbol was
	freed.
	(delete_symbol_from_ns): New, outline code from...
	(gfc_restore_last_undo_checkpoint): ... here.  Delete new symbols
	from two more namespaces.

gcc/testsuite/ChangeLog:

	* gfortran.dg/pr110996.f90: New test.