Do not configure QTHREADS. Do not define USE_COOP_THREADS. Changed

logic for thread package selection so that the default is
"coop-pthread" when -lpthread is found, "null" otherwise.

configure.in

@@ -639,73 +639,35 @@ fi
 
 ### What thread package has the user asked for?
 AC_ARG_WITH(threads, [  --with-threads          thread interface],
-            , with_threads=no)
+            , with_threads=yes)
 
-### Turn $with_threads into either the name of a threads package, like
-### `qt', or `no', meaning that threads should not be supported.
-AC_MSG_CHECKING(what kind of threads to support)
 case "$with_threads" in
-  "yes" | "qt" | "coop" | "")
+  "yes" | "coop-pthread" | "copt" | "coop" | "")
-    with_threads=qt
+    AC_CHECK_LIB(pthread, main,
+      LIBS="-lpthread $LIBS"
+      AC_DEFINE(USE_COPT_THREADS, 1,
+        [Define if using coop-pthread multithreading.])
+      with_threads="coop-pthreads",
+      with_threads="null")
+  ;;
+esac
+
+case "$with_threads" in
+  "coop-pthreads")
   ;;
   "no" | "null")
-    with_threads=null
+    AC_DEFINE(USE_NULL_THREADS, 1,
-  ;;
+      [Define if using one-thread 'multi'threading.])
-  "coop-pthreads" | "copt" )
+    with_threads="null-threads"
-    with_threads="coop-pthreads"
   ;;
   * )
     AC_MSG_ERROR(invalid value for --with-threads: $with_threads)
   ;;
 esac
+
+AC_MSG_CHECKING(what kind of threads to support)
 AC_MSG_RESULT($with_threads)
 
-## Make sure the threads package we've chosen is actually supported on
-## the present platform.
-case "${with_threads}" in
-  "qt" )
-    ## This configures the QuickThreads package, and sets or clears
-    ## the THREAD_PACKAGE variable if qthreads don't configure
-    ## correctly.  In that case, we fall back on null-threads.
-    QTHREADS_CONFIGURE
-   ;;
-  * )
-    THREAD_PACKAGE="${with_threads}"
-   ;;
-esac
-
-case "${THREAD_PACKAGE}" in
-  "QT" )
-    AC_DEFINE(USE_COOP_THREADS, 1,
-      [Define if using cooperative multithreading.])
-
-    AC_ARG_ENABLE(linuxthreads,
-      [  --disable-linuxthreads  disable linuxthreads workaround],,
-       enable_linuxthreads=yes)
-
-    ## Workaround for linuxthreads (optionally disabled)
-    if test $host_os = linux-gnu -a "$enable_linuxthreads" = yes; then
-      AC_DEFINE(GUILE_PTHREAD_COMPAT, 1,
-        [Define to enable workaround for COOP-linuxthreads compatibility.])
-      AC_CHECK_LIB(pthread, main)
-    fi
-
-  ;;
-  "null" | "" )
-    AC_DEFINE(USE_NULL_THREADS, 1,
-      [Define if using one-thread 'multi'threading.])
-  ;;
-  "coop-pthreads" )
-    AC_DEFINE(USE_COPT_THREADS, 1,
-      [Define if using coop-pthread multithreading.])
-    AC_CHECK_LIB(pthread, main)
-  ;;
-  * )
-    AC_MSG_ERROR(invalid value for THREAD_PACKAGE: ${THREAD_PACKAGE})
-  ;;
-esac
-
-
 ## Cross building	
 if test "$cross_compiling" = "yes"; then
   AC_MSG_CHECKING(cc for build)
@@ -864,10 +826,6 @@ AC_CONFIG_FILES([
   oop/goops/Makefile
   scripts/Makefile
   srfi/Makefile
-  qt/Makefile
-  qt/qt.h
-  qt/md/Makefile
-  qt/time/Makefile
   guile-config/Makefile
   doc/Makefile
   doc/ref/Makefile