updated doc with a couple of won't fix bugs

Summary:
adding the code example Drew found as a "won't fix" per our discussion

Test Plan:
doc

DiffCamp Revision: 129742
Reviewed By: andrewparoski
CC: hphp-diffs@lists, andrewparoski
Tasks:
#238897: bug in late static binding
#244920: HPHP doesn't preserve insane PHP behavior with respect to recursive
arrays.
#247054: XMLWriter/resource class cannot appear as type hints
#247963: assigning $GLOBALS

Revert Plan:
OK

doc/inconsistencies

@@ -31,6 +31,32 @@ a data member and then resetting it, it's order is not altered in foreach
 iteration. When unsetting then resetting to NULL, HipHop will be confused to
 think the property is still not present (bug).
 
+(3) $this handling of static method
+
+In PHP, $this may be passed into an unrelated class's static method. Here's an
+example,
+
+  <?php
+  class b {
+    public function bar() {
+      var_dump($this); // <-- $this is actually class "c" object
+      $this->baz();
+    }
+  }
+  class c {  // <-- note that "c" has nothing to do with "b"
+    public $x = 2;
+    public function foo() {
+      b::bar();
+    }
+    public function baz() {
+      echo "Hello!\n";
+    }
+  }
+  $obj = new c;
+  $obj->foo();
+
+In HipHop, $this will be NULL when doing this.
+
 3. Eval Issues
 
 (1) eval
@@ -60,7 +86,10 @@ Also, in PHP, $GLOBALS can be used as a regular variable, for example,
   $GLOBALS = 0;
   $x = $GLOBALS - 5;
 
-In HipHop, this is not allowed.
+  $g = $GLOBALS;
+  $g['x'] = 3;
+
+In HipHop, this is not allowed or not working.
 
 5. Dynamic declared constants
 
@@ -78,3 +107,18 @@ Can return classes in different order from PHP's.
 
 If an uninitialized variable is being used before it's assigned with a value,
 and this variable is inferred as integers, it will be 0, instead of null.
+
+(3) XMLWriter
+
+In PHP, XMLWriter class and its functions returned different types of objects,
+
+  <?php
+  function foo(XMLWriter $w) {}
+  $obj = new XMLWriter();
+  foo($obj); // <-- this one is actually okay
+  $obj2 = xmlwriter_open_memory(); // <-- just not this one
+  var_dump($obj, $obj2);
+  foo($obj2);
+
+In HipHop, they are the same.
+

doc/index.php

@@ -139,6 +139,7 @@ function format_document($doc) {
 
   $doc = preg_replace('/\n\n/', '<p>', $doc);      // paragraphs
   $doc = preg_replace('/<T>/', '&lt;T&gt;', $doc); // C++ templates
+  $doc = preg_replace('/<\?/', '&lt;?', $doc);     // PHP start tags
 
   // copyright notice
   $doc .= '<p>&nbsp;<table width="100%"><tr><td class="footer" align=right>'.