[pitivi] Show more info when intltool's IT_PROG_INTLTOOL macro is missing.

[Mathieu Duponchelle <mathieudu src gnome org>]

commit b5dcb8544f578119734ba3d9fdb5d8ffd47e98cd
Author: Alexandru Băluț <alexandru balut gmail com>
Date:   Mon Dec 16 21:32:10 2013 +0100

    Show more info when intltool's IT_PROG_INTLTOOL macro is missing.
    
    Fixes https://bugzilla.gnome.org/show_bug.cgi?id=583508

 configure.ac |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 69ccd27..7ff1905 100644
--- a/configure.ac
+++ b/configure.ac
@@ -51,7 +51,9 @@ GETTEXT_PACKAGE="pitivi"
 AC_SUBST([GETTEXT_PACKAGE])
 AC_DEFINE_UNQUOTED([GETTEXT_PACKAGE], "$GETTEXT_PACKAGE", [Gettext package])
 AM_GLIB_GNU_GETTEXT
-IT_PROG_INTLTOOL([0.35.0])
+m4_ifdef([IT_PROG_INTLTOOL],
+         [IT_PROG_INTLTOOL([0.35.0])],
+         [AC_MSG_ERROR("The IT_PROG_INTLTOOL m4 macro is not available. Install intltool.")])
 
 CONFIGURED_PYTHONPATH=$PYTHONPATH
 AC_SUBST(CONFIGURED_PYTHONPATH)