Bug 11447 - Check --enable-plugins value.

Extracted from trunk@34163. By jbrefort.

git-svn-id: svn+ssh://svn.abisource.com/svnroot/abiword/branches/ABI-3-0-0-STABLE@34225 bcba8976-2d24-0410-9c9c-aab3bd5fdfd6
Fixed configure when aiksaurus is not enabled.

Cherry-pick from trunk@34226. By jbrefort.

git-svn-id: svn+ssh://svn.abisource.com/svnroot/abiword/branches/ABI-3-0-0-STABLE@34227 bcba8976-2d24-0410-9c9c-aab3bd5fdfd6