Bump up the dependency on libepoxy

We are going to use new API to detect whether or not GLX is available
before calling GL API.

https://bugzilla.gnome.org/show_bug.cgi?id=775279

meson.build

@@ -37,7 +37,7 @@ wayland_req        = '>= 1.9.91'
 mirclient_req      = '>= 0.22.0'
 mircookie_req      = '>= 0.17.0'
 graphene_req       = '>= 1.5.1'
-epoxy_req          = '>= 1.0'
+epoxy_req          = '>= 1.4'
 cloudproviders_req = '>= 0.2.0'
 xkbcommon_req      = '>= 0.2.0'