Debian packaging: Add gettext to the build-depends line.

diff --git a/debian/control b/debian/control
index 1ca087d..da924ac 100644
--- a/debian/control
+++ b/debian/control
@@ -2,7 +2,7 @@
 Section: base
 Priority: required
 Maintainer: Theodore Y. Ts'o <tytso@mit.edu>
-Build-Depends: texi2html, texinfo, dc, debhelper (>= 4)
+Build-Depends: texi2html, gettext, texinfo, dc, debhelper (>= 4)
 Standards-Version: 3.5.9
 
 Package: e2fsck-static