a couple of bugs

[Ralf Wildenhues]

Hello,

besides Eric's reported failure of git Autoconf on OpenBSD (note to
self: fix should be tested with test 188 (AC_REPLACE_FUNCS)), I found a
couple more issues:

- test 28 (autotools and whitespace in file names) fails on systems with
  no installed Automake due to missing aclocal.  The empty aclocal.m4
  file should prevent it from being run, but the `aclocal --help' test
  in autoreconf seems to spoil that, bogusly.

- FreeBSD: autoupdate hangs on test 172 (AC_LANG_OBJC).  Dunno why yet,
  may be pilot error.

- IRIX: test 163 (AC_OPENMP) fails because the compiler creates a
  directory `rii_files' and doesn't remove it, which triggers the
  state-ls check.

I'll work on fixing them eventually, but don't mind being beaten to it.

Cheers,
Ralf