* directives.c (do_pragma_push_macro): New pragma handler.
(do_pragma_pop_macro): Likewise.
(_cpp_init_internal_pragmas): Add push_macro and
pop_macro handler to internal pragmas.
(lex_macro_node_from_str): Removed.
(cpp_push_definition): Replace lex_macro_node_from_str
by _cpp_lex_identifier.
(cpp_pop_definition): Likewise.
* internal.h (_cpp_lex_identifier): New prototype.
(def_pragma_macro): New structure.
(cpp_reader): New member pushed_macros.
* lex.c (_cpp_lex_identifier): New function.
(lex_identifier_intern): New function.
* init.c (cpp_create_reader): Initialize pushed_macros
member.
(cpp_destroy): Free elements in pushed_macros member.
* pch.c (_cpp_save_pushed_macros): New function.
(_cpp_restore_pushed_macros): Likewise.
(_cpp_restore_pushed_macros): Use _cpp_save_pushed_macros.
(cpp_read_state): Use _cpp_restore_pushed_macros.
* g++.dg/torture/pushpop_macro.C: New testcase.
* gcc.c-torture/execute/pushpop_macro.c: New testcase.
* gcc.dg/cpp/pragma-pop_macro-1.c: Allow test for all
targets.