autoconf: Fix call to AC_CONFIG_AUX_DIR.

The `pwd` parameter to AC_CONFIG_AUX_DIR is unnecessary, the default
value is $srcdir.

Additionally remove the AC_REVISION call.  It only added a comment and
is pointless without SVN tag replacements.

Change-Id: I99299a3217f095bddcb2edefb3b9af0ab147bc29