Custom help message when using argh

Help messages generated from argh is nearly useless and very hard to
customize. Fork argh and disable all code for generating help messages.

Use a closure to print the help message when handling EarlyExit.

native/src/Cargo.lock

@@ -23,8 +23,6 @@ dependencies = [
 [[package]]
 name = "argh"
 version = "0.1.10"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ab257697eb9496bf75526f0217b5ed64636a9cfafa78b8365c71bd283fcef93e"
 dependencies = [
  "argh_derive",
  "argh_shared",
@@ -33,8 +31,6 @@ dependencies = [
 [[package]]
 name = "argh_derive"
 version = "0.1.10"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b382dbd3288e053331f03399e1db106c9fb0d8562ad62cb04859ae926f324fa6"
 dependencies = [
  "argh_shared",
  "proc-macro2",
@@ -45,8 +41,6 @@ dependencies = [
 [[package]]
 name = "argh_shared"
 version = "0.1.10"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "64cb94155d965e3d37ffbbe7cc5b82c3dd79dd33bd48e536f73d2cfb8d85506f"
 
 [[package]]
 name = "atty"