configure.ac: Require GLib 2.31.10 and improve GIO check

configure.ac

@@ -511,10 +511,22 @@ CFLAGS="$save_cflags"
 dnl *** checks for dependency libraries ***
 
 dnl GLib
-GLIB_REQ=2.26
+GLIB_REQ=2.31.10
 
 AG_GST_GLIB_CHECK([$GLIB_REQ])
+
+dnl Check for GIO
 PKG_CHECK_MODULES(GIO, gio-2.0 >= $GLIB_REQ)
+GIO_MODULE_DIR="`$PKG_CONFIG --variable=giomoduledir gio-2.0`"
+AC_DEFINE_UNQUOTED(GIO_MODULE_DIR, "$GIO_MODULE_DIR",
+    [The GIO modules directory.])
+GIO_LIBDIR="`$PKG_CONFIG --variable=libdir gio-2.0`"
+    AC_DEFINE_UNQUOTED(GIO_LIBDIR, "$GIO_LIBDIR",
+        [The GIO library directory.])
+
+AC_SUBST(GIO_CFLAGS)
+AC_SUBST(GIO_LIBS)
+AC_SUBST(GIO_LDFLAGS)
 
 dnl Check for documentation xrefs
 GLIB_PREFIX="`$PKG_CONFIG --variable=prefix glib-2.0`"