Fix upper case matching in name mangling.

[crackcomm]

Note: It fixed messages but services and methods are not mangled properly:

module Greeter = struct
  module SayHello = struct
    let package_name = Some "ocxmr.greeter_async.proto"
    let service_name = "Greeter"
    let method_name = "SayHello"
    let name = "/ocxmr.greeter_async.proto.Greeter/SayHello"
    module Request = Hello_request
    module Response = Hello_reply
  end
  let sayHello = 
    (module Hello_request : Runtime'.Service.Message with type t = Hello_request.t ), 
    (module Hello_reply : Runtime'.Service.Message with type t = Hello_reply.t )
end

[andersfugmann]

Thanks for this PR. I've made some additional changes in #54, which supersedes this PR, so I will close it.