[gtranslator] Added itstool dependency to Meson

[Daniel Garcia Moreno <danigm src gnome org>]

commit cccbf5f5fc6e4ddd1fcaaed12a06ae2e2fc99912
Author: Daniel Mustieles <daniel mustieles contractor bbva com>
Date:   Mon Nov 5 11:24:28 2018 +0100

    Added itstool dependency to Meson

 meson.build | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/meson.build b/meson.build
index 54028faf..a2716fdf 100644
--- a/meson.build
+++ b/meson.build
@@ -127,6 +127,8 @@ if gtr_schemasdir == ''
   message(gtr_schemasdir)
 endif
 
+itstool = find_program  ('itstool')
+
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