WIP: Introduce libcryptsetup_cli.

Introducing new library supposed to be used in
cryptsetup tools and future cryptsetup loadable plugins

TODO:
  - distribution
  - cleanup header files
  - incorporate also plugin API?

lib/cli/libcryptsetup_cli.sym

@@ -0,0 +1,9 @@
+CRYPTSETUP_CLI_1.0 {
+	global:
+		crypt_cli_get_key;
+		crypt_cli_arg_set;
+		crypt_cli_arg_type;
+		crypt_cli_arg_value;
+	local:
+		*;
+};