[C++ PATCH] more TU parsing refactoring
https://gcc.gnu.org/ml/gcc-patches/2018-10/msg00788.html
* parser.h (struct cp_parser): Drop implicit_extern_c.
* parser.c (cp_debug_parser): Drop implicit_extern_c.
(cp_parser_new): Likewise.
(cp_parser_translation_unit): Handle implicit extern c here. Call
cp_parser_toplevel_declaration.
(cp_parser_toplevel_declaration): New, broken out of ...
(cp_parser_declaration_seq_opt): ... here. Call it. Drop
implicit extern C handling.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@265127 138bc75d-0d04-0410-961f-82ee72b054a4