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/dbrandom.c	Wed Feb 14 23:09:40 2018 +0800
+++ b/dbrandom.c	Thu Jul 20 19:38:26 2017 +0000
@@ -59,7 +59,7 @@
 	unsigned int readcount;
 	int ret = DROPBEAR_FAILURE;
 
-#ifdef DROPBEAR_PRNGD_SOCKET
+#if DROPBEAR_USE_PRNGD
 	if (prngd)
 	{
 		readfd = connect_unix(filename);
@@ -107,7 +107,7 @@
 			wantread = MIN(sizeof(readbuf), len-readcount);
 		}
 
-#ifdef DROPBEAR_PRNGD_SOCKET
+#if DROPBEAR_USE_PRNGD
 		if (prngd)
 		{
 			char egdcmd[2];
@@ -157,7 +157,7 @@
 
 static void write_urandom()
 {
-#ifndef DROPBEAR_PRNGD_SOCKET
+#if !DROPBEAR_USE_PRNGD
 	/* This is opportunistic, don't worry about failure */
 	unsigned char buf[INIT_SEED_SIZE];
 	FILE *f = fopen(DROPBEAR_URANDOM_DEV, "w");
@@ -185,7 +185,7 @@
 	/* existing state */
 	sha1_process(&hs, (void*)hashpool, sizeof(hashpool));
 
-#ifdef DROPBEAR_PRNGD_SOCKET
+#if DROPBEAR_USE_PRNGD
 	if (process_file(&hs, DROPBEAR_PRNGD_SOCKET, INIT_SEED_SIZE, 1) 
 			!= DROPBEAR_SUCCESS) {
 		dropbear_exit("Failure reading random device %s",