Merge remote-tracking branch 'origin/maint'

Merge remote-tracking branch 'origin/maint'

* origin/maint:
  maint: update release instructions
  maint: post-release administrivia
  version 2.5.90
  build: fix gen-ChangeLog call.
  gnulib: update.
  tests: fix SKIP_IF for Java.
  api.prefix: incompatible with %name-prefix.
  api.prefix: strengthen the tests and fix push-parsers.
  skeletons: style changes.
  NEWS: minor changes.
  api.prefix: improve the documentation for YYDEBUG.
  gnulib: update.

Conflicts:
	NEWS
	cfg.mk
	data/bison.m4
	doc/bison.texi
	m4/.gitignore
	tests/calc.at
	tests/headers.at