automake: update to 1.16.5.

New in 1.16.5:

* Bugs fixed

  - PYTHON_PREFIX and PYTHON_EXEC_PREFIX are now set according to
    Python's sys.* values only if the new configure option
    --with-python-sys-prefix is specified. Otherwise, GNU default values
    are used, as in the past. (The change in 1.16.3 was too incompatible.)

  - consistently depend on install-libLTLIBRARIES.

* Distribution

  - use const for yyerror declaration in bison/yacc tests.

(wiz)