Merge branch 'suffix-rules-work' into micro

Merge branch 'suffix-rules-work' into micro

* suffix-rules-work:
  NEWS: document fix for bug#14441
  Automake::Rule: consistently prepend underscore to private variables
  Automake::Rule: rename: suffix_rule() -> next_in_suffix_chain()
  Automake::Rule: adjust comments and POD according to previous changes
  Automake::Rule: make private variables lexically scoped
  suffix rules: better distinction between builtin and user-derived
  Automake::Rule: expose suffix rules as a function, not a scalar
  tests: expose automake bug#14441