currentcallview: fix GTK+ API incompatibility

gtk_css_provider_load_from_resource() was only added in GTK+ 3.16:
https://developer.gnome.org/gtk3/stable/GtkCssProvider.html#gtk-css-provider-load-from-resource

Debian 8 does not ship this version, so the client build currently
fails on this and other systems with < 3.16. We switch to using
load_from_data() version

note: you may have to clean your CMake build dir and re-run cmake
after this change, since our current cmake config doesn't work well
when gresource files are removed

Change-Id: I2a836a97cdea8b2d17bbb46f700a98d6eb153310
Reviewed-by: Guillaume Roguez <guillaume.roguez@savoirfairelinux.com>
diff --git a/src/currentcallview.cpp b/src/currentcallview.cpp
index 05f1c20..0bc3ca1 100644
--- a/src/currentcallview.cpp
+++ b/src/currentcallview.cpp
@@ -420,7 +420,10 @@
 
     // CSS styles
     auto provider = gtk_css_provider_new();
-    gtk_css_provider_load_from_resource(provider, "/cx/ring/RingGnome/currentcallview.css");
+    gtk_css_provider_load_from_data(provider,
+        ".smartinfo-block-style { color: #8ae234; background-color: rgba(1, 1, 1, 0.33); }",
+        -1, nullptr
+    );
     gtk_style_context_add_provider_for_screen(gdk_display_get_default_screen(gdk_display_get_default()),
                                               GTK_STYLE_PROVIDER(provider),
                                               GTK_STYLE_PROVIDER_PRIORITY_APPLICATION);