* iomanip.h: Use __extension__ for `extern' explicit template
instantiations.
* sinst.cc: Don't explicitly instantiation string_char_traits<char>.
* cinst.cc: Likewiwse, for complex<float>, complex<double>,
complex<long double>.
* extend.texi: Remove description of extension to explicit
instantiation that is now endorsed by standard C++.
* decl2.c (grok_array_decl): Add comment.
(mark_used): Don't instantiate an explicit instantiation.
* friend.c (make_friend_class): Remove bogus comment. Fix check
for partial specializations.
* pt.c (check_explicit_specialization): Don't
SET_DECL_EXPLICIT_INSTANTIATION here.
(mark_decl_instantiated): Or here.
(do_decl_instantiation): Do it here, instead. Add checks for
duplicate explicit instantiations, etc. Tidy.
(do_type_instantiation): Likewise.
(instantiate_decl): Improve comments. Complain about explicit
instantiations where no definition is available.
* cp-tree.h (ansi_null_node): Remove.
* call.c (build_over_call): Warn about converting NULL to an
arithmetic type.
* cvt.c (build_expr_type_conversion): Likewise. Use
null_ptr_cst_p instead of expanding it inline.
* decl.c (ansi_null_node): Remove.
(init_decl_processing): Make null_node always have integral type.
* except.c (build_throw): Warn about converting NULL to an
arithmetic type.
* lex.c (init_parse): Remove handling of ansi_null_node.
* pt.c (type_unification_real): Don't convert NULL to void* type.
* typeck.c (build_binary_op_nodefault): Fix NULL warnings.
(convert_for_assignment): Warn about converting NULL to an
arithmetic type.
(convert_for_initialization): Likewise.
From-SVN: r21915
