password utils: improve --help, make DEFAULT_PASSWD_ALGO visible if CHPASSWD

Was:
    $ cryptpw --help
    ...
    Print crypt(3) hashed PASSWORD

        -P,--password-fd=N	Read password from fd N
        -m,--method=TYPE	Encryption method
        -S,--salt=SALT

User: "What methods exist? which one os default?"

Now:
    Print crypt(3) hashed PASSWORD

        -P,--password-fd N	Read password from fd N
        -m,--method TYPE	des,md5,sha256/512 (default des)
        -S,--salt SALT

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/include/usage.src.h b/include/usage.src.h
index 78beccf..00369df 100644
--- a/include/usage.src.h
+++ b/include/usage.src.h
@@ -14,6 +14,14 @@
 
 #define NOUSAGE_STR "\b"
 
+#if !ENABLE_USE_BB_CRYPT || ENABLE_USE_BB_CRYPT_SHA
+# define CRYPT_METHODS_HELP_STR "des,md5,sha256/512" \
+	" (default "CONFIG_FEATURE_DEFAULT_PASSWD_ALGO")"
+#else
+# define CRYPT_METHODS_HELP_STR "des,md5" \
+	" (default "CONFIG_FEATURE_DEFAULT_PASSWD_ALGO")"
+#endif
+
 INSERT
 
 #define busybox_notes_usage \