Bug 1346622 - Add a preference for the "troubleshooting" URL and use it in the help. r=IanN

With this, the link in the help welcome page can point to the
version-specific troubleshooting information directly, instead of
relying on the /doc/troubleshooting server-side redirect.

suite/app/profile/suite-prefs.js

@@ -488,6 +488,7 @@ pref("shell.checkDefaultClient", true);
 pref("shell.checkDefaultApps", 3);
 
 pref("app.releaseNotesURL", "chrome://branding/locale/brand.properties");
+pref("app.troubleshootingURL", "chrome://branding/locale/brand.properties");
 pref("app.vendorURL", "chrome://branding/locale/brand.properties");
 
 // Base URL for web-based support pages.

suite/branding/seamonkey/locales/en-US/brand.properties

@@ -8,4 +8,5 @@ brandShorterName=SeaMonkey
 vendorShortName=SeaMonkey e.V.
 sidebarName=Sidebar
 app.releaseNotesURL=https://www.seamonkey-project.org/releases/seamonkey%VERSION%/
+app.troubleshootingURL=https://www.seamonkey-project.org/releases/seamonkey%VERSION%/#troubleshooting
 app.vendorURL=https://www.seamonkey-project.org/

suite/locales/en-US/chrome/common/help/welcome_help.xhtml

@@ -48,7 +48,7 @@
 
   <tr valign="top">
     <td>
-      <p><strong><a href="http://www.seamonkey-project.org/doc/troubleshooting">Troubleshooting</a></strong></p>
+      <p><strong><a href="x-moz-url-link:app.troubleshootingURL">Troubleshooting</a></strong></p>
 
       <p>Answers to some of the most frequently encountered problems.</p>
     </td>