No GUdev on OpenBSD (XXX add HAVE_GUDEV to meson_options.txt)

Index: panels/common/meson.build
--- panels/common/meson.build.orig
+++ panels/common/meson.build
@@ -86,18 +86,16 @@ liblanguage_dep = declare_dependency(
 )
 
 gsd_headers = [
-  'gsd-device-manager.h',
   'gsd-input-helper.h'
 ]
 
 gsd_sources = [
-  'gsd-device-manager.c',
   'gsd-input-helper.c'
 ]
 
 sources = common_sources + files(gsd_sources)
 
-deps = common_deps + [ gudev_dep ]
+deps = common_deps
 
 libdevice = static_library(
   'device',