options: Complete the transition to numeric toggles (`#if') For the sake of review, this commit alters only the code; the affiliated comments within the source files also need to be updated, but doing so now would obscure the operational changes that have been made here. * All on/off options have been switched to the numeric `#if' variant; that is the only way to make this `default_options.h.in' thing work in a reasonable manner. * There is now some very minor compile-time checking of the user's choice of options. * NO_FAST_EXPTMOD doesn't seem to be used, so it has been removed. * ENABLE_USER_ALGO_LIST was supposed to be renamed DROPBEAR_USER_ALGO_LIST, and this commit completes that work. * DROPBEAR_FUZZ seems to be a relatively new, as-yet undocumented option, which was added by the following commit: commit 6e0b539e9ca0b5628c6c5a3d118ad6a2e79e8039 Author: Matt Johnston <[email protected]> Date: Tue May 23 22:29:21 2017 +0800 split out checkpubkey_line() separately It has now been added to `sysoptions.h' and defined as `0' by default. * The configuration option `DROPBEAR_PASSWORD_ENV' is no longer listed in `default_options.h.in'; it is no longer meant to be set by the user, and is instead left to be defined in `sysoptions.h' (where it was already being defined) as merely the name of the environment variable in question: DROPBEAR_PASSWORD To enable or disable use of that environment variable, the user must now toggle `DROPBEAR_USE_DROPBEAR_PASSWORD'. * The sFTP support is now toggled by setting `DROPBEAR_SFTPSERVER', and the path of the sFTP server program is set independently through the usual SFTPSERVER_PATH.

-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY-----