Fix up create*Window functions to be more mobile-friendly

I was surprised to see that the site is already pretty mobile-friendly.
The main issue was the quick reply, new thread, and report
windows - they were all hard-coded to be 500px, 500px, and 360px wide
respectively. Now, those hard-coded widths are the default but if the
viewport is thinner than that, the new window will size itself down with
some padding.

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

board/static/board/post.js

@@ -73,10 +73,11 @@ function openReplyWindow(replyUrl) {
         return getReplyWindow();
     }
 
+    let width = Math.min(window.top.innerWidth - 20, 500);
     let replyWindow = window.top.jsFrame.create({
         title: "New Reply",
         name: replyWindowName,
-        width: 500,
+        width: width,
         url: replyUrl
     });
     $(replyWindow.iframe, "iframe").on("load", () => {
@@ -123,10 +124,11 @@ function openPostWindow(postUrl) {
     if (window.top.jsFrame.containsWindowName(postWindowName)) {
         return;
     }
+    let width = Math.min(window.top.innerWidth - 20, 500);
     let postWindow = window.top.jsFrame.create({
         title: "New Thread",
         name: postWindowName,
-        width: 500,
+        width: width,
         url: postUrl,
     });
     $(postWindow.iframe, "iframe").on("load", () => {
@@ -153,10 +155,11 @@ function openReportWindow(reportUrl) {
     if (window.top.jsFrame.containsWindowName(reportWindowName)) {
         getReportWindow().closeFrame();
     }
+    let width = Math.min(window.top.innerWidth - 20, 360);
     let reportWindow = window.top.jsFrame.create({
         url: reportUrl,
         name: reportWindowName,
-        width: 360,
+        width: width,
     });
     $(reportWindow.iframe, "iframe").on("load", () => {
         fitWindowToContent(reportWindow);