Merge remote-tracking branch 'origin/maint'

Merge remote-tracking branch 'origin/maint'

* origin/maint:
  maint: formatting changes.
  tests: support api.prefix.
  tests: pacify font-lock-mode.
  tests: remove test covered elsewhere.
  tests: factor the declaration/definition of yyerror and yylex.
  regen.
  tests: portability issues.
  tests: call the parser from another compilation unit.
  glr.c, yacc.c: declare yydebug in the header.
  skeletons: use header guards.
  tests: improve AT_FULL_COMPILE.
  tests: reorder.
  tests: strengthen the test on generated headers inclusion
  yacc.c: instead of duplicating y.tab.h inside y.tac.c, include it.
  yacc.c: factor.

Conflicts:
	NEWS
	data/glr.c
	data/yacc.c
	src/parse-gram.c
	src/parse-gram.h
	tests/conflicts.at
	tests/regression.at