[securemail] Upgrade Composer dependencies to fix PHP8 issue

- Upgrading phpseclib/phpseclib (2.0.4 => 2.0.34)
- Upgrading singpolyma/openpgp-php (0.3.0 => 0.5.0)

securemail/vendor/singpolyma/openpgp-php/.travis.dhall

@@ -0,0 +1,30 @@
+let Prelude = https://prelude.dhall-lang.org/v17.0.0/package.dhall
+let phpseclib = \(max: Natural) -> \(filter: (Natural -> Bool)) ->
+	Prelude.List.map Natural Text
+		(\(m: Natural) -> "PHPSECLIB='2.0.${Prelude.Natural.show m}'")
+		(Prelude.List.filter Natural filter (Prelude.Natural.enumerate max))
+let Exclusion = { php: Text, env: Text }
+in
+{
+	language = "php",
+	php = [
+		"7.3",
+		"7.4",
+		"8.0"
+	],
+	dist = "xenial",
+	env = [
+		"PHPSECLIB='^2.0 !=2.0.8'"
+	] # (phpseclib 28 (\(m: Natural) -> Prelude.Bool.not (Prelude.Natural.equal m 8))
+	),
+	matrix = {
+		exclude = Prelude.List.concatMap Text Exclusion (\(php: Text) ->
+			Prelude.List.map Text Exclusion (\(env: Text) ->
+				{ php = php, env = env }
+			) (phpseclib 7 (\(_: Natural) -> True))
+		) ["7.3", "7.4", "8.0"],
+		fast_finish = True
+	},
+	before_script = ''
+	sed -i "s/\"phpseclib\/phpseclib\": \"[^\"]*/\"phpseclib\/phpseclib\": \"$PHPSECLIB/" composer.json && composer install --prefer-source''
+}