[seahorse] Meson: fix libseahorse not finding the right headers.

[Niels De Graef <nielsdg src gnome org>]

commit fb6a976a67c116dc0f2d3691e5d74795bcfe45bf
Author: Niels De Graef <nielsdegraef gmail com>
Date:   Tue Nov 21 19:29:59 2017 +0100

    Meson: fix libseahorse not finding the right headers.

 libseahorse/meson.build |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/libseahorse/meson.build b/libseahorse/meson.build
index a3450f6..9313fa8 100644
--- a/libseahorse/meson.build
+++ b/libseahorse/meson.build
@@ -40,6 +40,7 @@ libseahorse_deps = [
 libseahorse_lib = static_library('libseahorse',
   libseahorse_sources,
   dependencies: libseahorse_deps,
+  include_directories: include_directories('..'),
 )
 
 libseahorse_dep = declare_dependency(