Fix MingW threading support.

git-svn-id: file:///fltk/svn/fltk/branches/branch-1.1@4731 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

configure.in

@@ -581,10 +581,13 @@ case $uname in
 	    GLDEMOS=""
 	fi
 
-	if test x$have_pthread = xyes; then
-	    AC_DEFINE(HAVE_PTHREAD)
+	if test "x$enable_threads" = xyes; then
+	    if test x$have_pthread = xyes; then
+		AC_DEFINE(HAVE_PTHREAD)
+	    fi
+
 	    THREADS="threads.exe"
-	fi
+        fi
 
 	# Don't make symlinks since Windows is not case sensitive.
 	if test "x$with_links" != xyes; then