Allow compilation without internationalization (gettext dependency)

[patrickdepinguin]

Currently, libuio requires gettext due to the use of internationalization of messages in lsuio.
For embedded systems that just need the libuio library, this is a heavy dependency wrt compilation time.

I am currently using a patch that stubs out the internationalization alone (see below).
Since I guess you would not just accept that patch as it is not flexible, here are two alternative approaches:

1. provide a configure option to enable/disable internationalization support
2. provide a configure option to enable/disable the building of the userspace tools lsuio and readuio. When these tools are not requested, there should also not be a gettext dependency.

What are your thoughts on this?
Thanks.

diff --git a/Makefile.am b/Makefile.am
index 50d2fd2..667fd91 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1,5 +1,3 @@
-SUBDIRS = po
-
 pkgconfigdir = $(datadir)/pkgconfig
 pkgconfig_DATA = libuio.pc
 
diff --git a/configure.ac b/configure.ac
index f7fb40f..b01b2b7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -38,10 +38,6 @@ AS_IF([test "x$with_glib" != "xno"], [
    AC_DEFINE([USE_GLIB], [1], [use glib-2.0])
 ])
 
-dnl i18n makros.
-AM_GNU_GETTEXT([external])
-AM_GNU_GETTEXT_VERSION([0.17])
-
 dnl with or without -Werror
 AC_ARG_WITH([werror],
             [AS_HELP_STRING([--without-werror],
@@ -56,4 +52,4 @@ AC_OUTPUT([Makefile
 	libuio.dox
 	libuio-uninstalled.pc
 	libuio.pc
-	po/Makefile.in])
+	])