This patch adds some default values so that SpamAssassin-only users of amavisd-new do not have
to add any new configuration options. Hopefully, amavisd-new with this patch will behave as
amavisd-new 2.4.1.

1. @load_spamscanners defaults to SpamAssassin now. Everybody who uses only SpamAssassin 
   does not have to add this command to the config file.
2. "@load_spamscanners = ()" has the same effect as "@bypass_spam_checks_maps  = (1);"
3. If a recipient has no explicitely specified spam scanner (in "$spamscanner_tables"),
   the default scanner is used. The default scanner is the first scanner in 
   @load_spamscanners.

--- original/amavisd	2006-05-21 12:23:13.000000000 +0200
+++ modified/amavisd	2006-05-22 22:04:39.000000000 +0200
@@ -640,6 +640,8 @@
 $sa_debug = undef;
 $sa_timeout = 30;           # timeout in seconds for a call to SpamAssassin
 
+@load_spamscanners = ( 'SpamAssassin' );
+
 $file = 'file';  # path to the file(1) utility for classifying contents
 
 # provide names for content categories - to be used only for logging,
@@ -9298,9 +9300,12 @@
   ${$ref} = 1;
 }
 
+sub noSpamscannersLoaded() {
+  return scalar(@{ca('load_spamscanners')}) < 1;
+}
 
 my($bpscm) = ca('bypass_spam_checks_maps');
-if (@$bpscm && !ref($bpscm->[0]) && $bpscm->[0]) {
+if ((@$bpscm && !ref($bpscm->[0]) && $bpscm->[0]) or noSpamscannersLoaded()) {
   # do a simple-minded test to make it easy to turn off spam checks
   $extra_code_antispam = undef;
   $extra_code_antispam_dspam = undef;
@@ -14475,7 +14480,7 @@
 
 # called at startup, before chroot and before main fork
 sub init_pre_chroot() {
-  if (! $Amavis::extra_code_antispam) {
+  if (not $Amavis::extra_code_antispam) {
     do_log(0, "SpamControl: antispam code not loaded, no spam scanning");
     %spamscanners = undef;
   } else {
@@ -14529,7 +14534,10 @@
     $spamscanner = setScannerIfNotSet($name, $spamscanner);
   }
   if (not defined $spamscanner) {  # fall back to default scanner!
-    $spamscanner = "SpamAssassin"; # TODO: make default scanner configurable
+    # The first scanner in the list "load_spamscanners" is considered to be
+    # the default scanner. This scanner is used for all users which do not
+    # have an explicit entry in "spamscanner_tables".
+    $spamscanner = ${ca('load_spamscanners')}[0];
   }
   return $spamscanner;
 }