maint: fix some syntax-check issues.

	* cfg.mk (local-checks-to-skip): Remove
	sc_prohibit_quotearg_without_use, sc_prohibit_strcmp,
	sc_unmarked_diagnostics, sc_useless_cpp_parens.
	(sc_unmarked_diagnostics): Skip DJGPP.
	* data/yacc.c, src/LR0.c, src/closure.c,
	* src/flex-scanner.h, src/gram.c, src/lalr.c,
	* src/print-xml.c, src/print.c, src/print_graph.c,
	* src/reader.c, src/reduce.c, src/tables.c:
	Don't use parens with cpp's defined.
	Remove useless includes.