Fix typo.  Backport if anyone cares. :-)
diff --git a/configure.in b/configure.in
index 8baa149..cca20a8 100644
--- a/configure.in
+++ b/configure.in
@@ -235,7 +235,7 @@
   # On Mac OS X 10.4, defining _POSIX_C_SOURCE or _XOPEN_SOURCE
   # disables platform specific features beyond repair.
   # On Mac OS X 10.3, defining _POSIX_C_SOURCE or _XOPEN_SOURCE 
-  # has no effect, don't bother defineing them
+  # has no effect, don't bother defining them
   Darwin/@<:@78@:>@.*)
     define_xopen_source=no
     ;;