simplify formbuilder stylesheet specification

Since all forms are wrapped in a template that defines the actual
stylesheets, formbuilder just has to be told to turn on stylesheet mode,
not what file is the style sheet.

IkiWiki/CGI.pm

@@ -108,7 +108,7 @@ sub cgi_signin ($$) {
 		action => $config{cgiurl},
 		header => 0,
 		template => {type => 'div'},
-		stylesheet => baseurl()."style.css",
+		stylesheet => 1,
 	);
 	my $buttons=["Login"];
 	
@@ -187,7 +187,7 @@ sub cgi_prefs ($$) {
 		params => $q,
 		action => $config{cgiurl},
 		template => {type => 'div'},
-		stylesheet => baseurl()."style.css",
+		stylesheet => 1,
 		fieldsets => [
 			[login => gettext("Login")],
 			[preferences => gettext("Preferences")],

IkiWiki/Plugin/remove.pm

@@ -103,7 +103,7 @@ sub confirmation_form ($$) {
 		javascript => 0,
 		params => $q,
 		action => $config{cgiurl},
-		stylesheet => IkiWiki::baseurl()."style.css",
+		stylesheet => 1,
 		fields => [qw{do page}],
 	);
 	

IkiWiki/Plugin/rename.pm

@@ -126,7 +126,7 @@ sub rename_form ($$$) {
 		javascript => 0,
 		params => $q,
 		action => $config{cgiurl},
-		stylesheet => IkiWiki::baseurl()."style.css",
+		stylesheet => 1,
 		fields => [qw{do page new_name attachment}],
 	);
 	

IkiWiki/Plugin/websetup.pm

@@ -293,7 +293,7 @@ sub showform ($$) {
 		],
 		action => $config{cgiurl},
 		template => {type => 'div'},
-		stylesheet => IkiWiki::baseurl()."style.css",
+		stylesheet => 1,
 	);
 	
 	$form->field(name => "do", type => "hidden", value => "setup",