No declaration for isblank

[Neil Jerram]

Compiling current CVS on Debian Etch:

...
gcc -DHAVE_CONFIG_H -I. -I.. -I.. -I.. -I../lib -I../lib -pthread -g -O2 -Wall 
-Wmissing-prototypes -Werror -MT libguile_la-srfi-14.lo -MD -MP -MF 
.deps/libguile_la-srfi-14.Tpo -c srfi-14.c  -fPIC -DPIC -o 
.libs/libguile_la-srfi-14.o
cc1: warnings being treated as errors
srfi-14.c: In function 'scm_srfi_14_compute_char_sets':
srfi-14.c:1532: warning: implicit declaration of function 'isblank'
make[3]: *** [libguile_la-srfi-14.lo] Error 1
make[3]: Leaving directory 
`/home/neil/Organized/SW/Guile/guile-cvs-head/guile/guile-core/libguile'
...

The patch below cures this, but is it correct?

Regards,
        Neil

--- srfi-14.c   29 Jul 2007 14:58:21 -0000      1.6
+++ srfi-14.c   19 Sep 2007 21:25:08 -0000
@@ -17,6 +17,8 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+#define _GNU_SOURCE
+
 #ifdef HAVE_CONFIG_H
 #  include <config.h>
 #endif