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.

--- a/keyimport.c	Wed Feb 14 23:09:40 2018 +0800
+++ b/keyimport.c	Thu Jul 20 19:38:26 2017 +0000
@@ -870,7 +870,7 @@
 		 */
 		numbers[0].start = zero; numbers[0].bytes = 1; zero[0] = '\0';
 
-	#ifdef DROPBEAR_RSA
+	#if DROPBEAR_RSA
 		if (key->type == DROPBEAR_SIGNKEY_RSA) {
 
 			if (key->rsakey->p == NULL || key->rsakey->q == NULL) {
@@ -966,7 +966,7 @@
 		}
 	#endif /* DROPBEAR_RSA */
 
-	#ifdef DROPBEAR_DSS
+	#if DROPBEAR_DSS
 		if (key->type == DROPBEAR_SIGNKEY_DSS) {
 
 			/* p */