Merge branch 'branch-1.13.2' into maint

Merge branch 'branch-1.13.2' into maint

* branch-1.13.2:
  docs: issues with configure substitutions in TESTS
  tests: avoid possible autotools caching issues (automake bug#13832)
  docs: add myself and Ralf Wildenhues as authors
  authors: add myself
  dry-run: don't get confused by '-I' option
  tests: avoid a spurious failure with the Korn Shell
  dry-run: with GNU make, prefer $(MFLAGS) over $(MAKEFLAGS)
  header vars: can determine whether we are running under GNU make
  NEWS: improve wording for automake bug#13514 fix
  NEWS: document fix for automake bug#13514