[various] Fix hook function type-hints

- Address https://friendica.xyz/display/adf174d5-1562-b8d8-53d7-ffd690518338

mathjax/mathjax.php

@@ -50,7 +50,7 @@ function mathjax_settings(App $a, array &$data)
 	];
 }
 
-function mathjax_footer(App $a, array &$b)
+function mathjax_footer(App $a, string &$b)
 {
 	//  if the visitor of the page is not a local_user, use MathJax
 	//  otherwise check the users settings.

pageheader/pageheader.php

@@ -17,7 +17,7 @@ function pageheader_install() {
     Hook::register('page_content_top', __FILE__, 'pageheader_fetch');
 }
 
-function pageheader_addon_admin(App &$a, &$s)
+function pageheader_addon_admin(App &$a, string &$s)
 {
 	if (!$a->isSiteAdmin()) {
 		return;
@@ -52,7 +52,7 @@ function pageheader_addon_admin_post(App $a)
 	}
 }
 
-function pageheader_fetch(App $a, array &$b)
+function pageheader_fetch(App $a, string &$b)
 {
 	if(file_exists('pageheader.html')){
 		$s = file_get_contents('pageheader.html');

saml/saml.php

@@ -80,12 +80,12 @@ function saml_install()
 	Hook::register('footer', __FILE__, 'saml_footer');
 }
 
-function saml_head(App $a, array &$b)
+function saml_head(App $a, string &$b)
 {
 	DI::page()->registerStylesheet(__DIR__ . '/saml.css');
 }
 
-function saml_footer(App $a, array &$b)
+function saml_footer(App $a, string &$b)
 {
 	$fragment = addslashes(BBCode::convert(DI::config()->get('saml', 'settings_statement')));
 	$b .= <<<EOL

showmore_dyn/showmore_dyn.php

@@ -24,12 +24,12 @@ function showmore_dyn_install()
 	Hook::register('addon_settings_post',  __FILE__, 'showmore_dyn_settings_post');
 }
 
-function showmore_dyn_head(App $a, array &$b)
+function showmore_dyn_head(App $a, string &$b)
 {
 	DI::page()->registerStylesheet(__DIR__ . '/showmore_dyn.css');
 }
 
-function showmore_dyn_footer(App $a, array &$b)
+function showmore_dyn_footer(App $a, string &$b)
 {
 	DI::page()->registerFooterScript(__DIR__ . '/showmore_dyn.js');
 }