Better error recovery for merge-conflict markers

Better error recovery for merge-conflict markers

gcc/c-family/ChangeLog:
	* c-common.h (conflict_marker_get_final_tok_kind): New prototype.
	* c-lex.c (conflict_marker_get_final_tok_kind): New function.

gcc/c/ChangeLog:
	* c-parser.c (struct c_parser): Expand array "tokens_buf" from 2
	to 4.
	(c_parser_peek_nth_token): New function.
	(c_parser_peek_conflict_marker): New function.
	(c_parser_error): Detect conflict markers and report them as such.

gcc/cp/ChangeLog:
	* parser.c (cp_lexer_peek_conflict_marker): New function.
	(cp_parser_error): Detect conflict markers and report them as
	such.

gcc/testsuite/ChangeLog:
	* c-c++-common/conflict-markers-1.c: New testcase.
	* c-c++-common/conflict-markers-2.c: Likewise.
	* c-c++-common/conflict-markers-3.c: Likewise.
	* c-c++-common/conflict-markers-4.c: Likewise.
	* c-c++-common/conflict-markers-5.c: Likewise.
	* c-c++-common/conflict-markers-6.c: Likewise.
	* c-c++-common/conflict-markers-7.c: Likewise.
	* c-c++-common/conflict-markers-8.c: Likewise.
	* c-c++-common/conflict-markers-9.c: Likewise.
	* c-c++-common/conflict-markers-10.c: Likewise.
	* c-c++-common/conflict-markers-11.c: Likewise.
	* g++.dg/conflict-markers-1.C: Likewise.

From-SVN: r231712