Add support for empty closing tags

Summary:
<foo>bar</> is now valid syntax. "</>" will just close whatever tag happens to
be open at the time. This mimics the behavior of a subset of SGML's SHORTTAG
directive.

Reviewed By: dcorson

Test Plan: xhpize + various clients of XHP

Revert: OK

ext.hpp

@@ -4,7 +4,7 @@
 #endif
 #include "php.h"
 
-#define PHP_XHP_VERSION "1.3.3"
+#define PHP_XHP_VERSION "1.3.5"
 #define PHP_XHP_EXTNAME "xhp"
 
 extern zend_module_entry xhp_module_entry;

xhp/parser.y

@@ -158,7 +158,8 @@ static void replacestr(string &source, const string &find, const string &rep) {
 
 %token T_XHP_WHITESPACE
 %token T_XHP_TEXT
-%token T_XHP_LESS_THAN_DIV
+%token T_XHP_LT_DIV
+%token T_XHP_LT_DIV_GT
 %token T_XHP_ATTRIBUTE
 %token T_XHP_CATEGORY
 %token T_XHP_CHILDREN
@@ -1468,7 +1469,7 @@ xhp_tag_open:
 ;
 
 xhp_tag_close:
-  T_XHP_LESS_THAN_DIV xhp_label_no_space '>' {
+  T_XHP_LT_DIV xhp_label_no_space '>' {
     pop_state(); // XHP_CHILD_START
     if (yyextra->peekTag() != $2.c_str()) {
       string e1 = $2.c_str();
@@ -1487,6 +1488,15 @@ xhp_tag_close:
     }
     $$ = "))";
   }
+| T_XHP_LT_DIV_GT {
+    // empty end tag -- SGML SHORTTAG
+    pop_state(); // XHP_CHILD_START
+    yyextra->popTag();
+    if (yyextra->haveTag()) {
+      set_state(XHP_CHILD_START);
+    }
+    $$ = "))";
+  }
 ;
 
 xhp_tag_start:

xhp/scanner.l

@@ -607,7 +607,11 @@ NEWLINE ("\r\n"|"\n"|"\r")
   }
   {WHITESPACE}*"</" {
     yy_scan_newlines(yytext, yyg);
-    tok(T_XHP_LESS_THAN_DIV);
+    tok(T_XHP_LT_DIV);
+  }
+  {WHITESPACE}*"</>" {
+    yy_scan_newlines(yytext, yyg);
+    tok(T_XHP_LT_DIV_GT);
   }
 }