Move auxiliary build scripts into separate directory.

* configure.ac: Move auxiliary build scripts into separate directory
`build-aux'.

Signed-off-by: Justus Winter <justus@g10code.com>

configure.ac

@@ -80,6 +80,7 @@ BUILD_REVISION=svn_revision
 PACKAGE=$PACKAGE_NAME
 VERSION=$PACKAGE_VERSION
 
+AC_CONFIG_AUX_DIR([build-aux])
 AC_CONFIG_SRCDIR([src/cryptoki.h])
 AC_CONFIG_HEADER([config.h])
 AC_CONFIG_MACRO_DIR(m4)