Raise error on SRFI-18 load if Guile built without threading support

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

srfi/ChangeLog

@@ -1,3 +1,8 @@
+2008-08-30  Julian Graham <joolean@gmail.com>
+
+       * srfi-18.scm: Raise error if Guile not built with threading
+       support.
+
 2008-08-25  Ludovic Courtès  <ludo@gnu.org>
 
 	* Makefile.am (AM_CFLAGS): New.

srfi/srfi-18.scm

@@ -89,6 +89,9 @@
 	    make-condition-variable
 	    raise))
 
+(if (not (provided? 'threads))
+    (error "SRFI-18 requires Guile with threads support"))
+
 (cond-expand-provide (current-module) '(srfi-18))
 
 (define (check-arg-type pred arg caller)

test-suite/tests/srfi-18.test

@@ -19,10 +19,10 @@
 ;;;; Boston, MA 02110-1301 USA
 
 (define-module (test-suite test-srfi-18)
-  #:use-module (test-suite lib)
-  #:use-module (srfi srfi-18))
+  #:use-module (test-suite lib))
 
 (and (provided? 'threads)
+     (use-modules (srfi srfi-18))
 
 (with-test-prefix "current-thread"