link against gthread on old glib

if glib is ancient, link against gthread ... fixes centos5 build

thanks re-boot

.gitignore

@@ -1,4 +1,5 @@
 test-driver
+po/vips*.pot
 vips-*.tar.gz
 doc/reference/setup-build.stamp
 doc/reference/tmpl-build.stamp

ChangeLog

@@ -1,5 +1,6 @@
 14/5/13 started 7.32.4
 - icc import and export could segv on very wide images
+- fix centos 5 build, thanks re-boot
 
 16/4/13 started 7.32.3
 - rename GETTEXT_PACKAGE as vips7.32 to help Debian (thanks Jay)

configure.ac

@@ -325,7 +325,9 @@ PKG_CHECK_MODULES(THREADS, glib-2.0 >= 2.32,[
   AC_DEFINE(HAVE_PRIVATE_INIT,1,[define if your glib has G_PRIVATE_INIT().])
   AC_DEFINE(HAVE_VALUE_GET_SCHAR,1,[define if your glib has g_value_get_schar().])
   ],[
-     # no action if not found
+    # the old threading system ... we need to link against gthread
+    PKG_CHECK_MODULES(GTHREAD, gthread-2.0)
+    PACKAGES_USED="$PACKAGES_USED gthread-2.0"
   ]
 )