[json-glib] build: convert interface_age to int

[Igor Gnatenko <ignatenko src gnome org>]

commit d508a0af61bf0e092664a98726fcdf2b7f98d5a8
Author: Igor Gnatenko <ignatenko src gnome org>
Date:   Mon Mar 13 14:22:08 2017 +0100

    build: convert interface_age to int
    
    Meson encountered an error in file meson.build, line 30, column 0:
    Subtraction works only with integers.
    
    Signed-off-by: Igor Gnatenko <ignatenko src gnome org>

 meson.build |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/meson.build b/meson.build
index 1cc1868..29d59da 100644
--- a/meson.build
+++ b/meson.build
@@ -20,7 +20,7 @@ soversion = 0
 if json_version_micro.to_int().is_odd()
   json_interface_age = 0
 else
-  json_interface_age = json_version_micro
+  json_interface_age = json_version_micro.to_int()
 endif
 
 # maintaining compatibility with the previous libtool versioning