Fix glitches and stuff

Summary:
- abstract elements are now allowed
- fix `element` keyword if no markup appears in the file
- allow <a\nhref="..." />; where \n is an actualy linebreak
- fix certain heredocs

Reviewed By: no one

Test Plan: master_include.php \ test cases from evan

Revert Plan: ok

ext.cpp

@@ -95,7 +95,14 @@ static zend_op_array* xhp_compile_file(zend_file_handle* f, int type TSRMLS_DC)
         maybe_xhp = 1;
         break;
       }
-    } else if (*ii == '/' && ii[1] == '>') { // <a />
+    } else if (*ii == '/') { // <a />
+      if (ii[1] == '>') {
+        maybe_xhp = 1;
+        break;
+      }
+    } else if (*ii == 'e' && ii[1] == 'l' && ii[2] == 'e' && ii[3] == 'm' && ii[4] == 'e' && ii[5] == 'n' && ii[6] == 't') {
+//    } else if (memcmp(ii, "element", 7)) {
+      // why is this faster than memcmp? i'm bad at computers and i don't know.
       maybe_xhp = 1;
       break;
     }

xhp_parser.y

@@ -971,8 +971,17 @@ xhp_whitespace_hack:
 
 // element declarations
 xhp_element_declaration:
-  t_ELEMENT { yy_push_state(PHP_NO_RESERVED_WORDS); } xhp_label xhp_whitespace_hack xhp_element_extends xhp_element_implements t_LCURLY class_statement_list t_RCURLY {
-    $$ = cr("class xhp_") + $3 + " " + $5 + " " + $6 + "{" + $8 + cr("}");
+  xhp_element_entry { yy_push_state(PHP_NO_RESERVED_WORDS); } xhp_label xhp_whitespace_hack xhp_element_extends xhp_element_implements t_LCURLY class_statement_list t_RCURLY {
+    $$ = $1 + $3 + " " + $5 + " " + $6 + "{" + $8 + cr("}");
+  }
+;
+
+xhp_element_entry:
+  t_ELEMENT {
+    $$ = cr("class xhp_");
+  }
+| t_ABSTRACT t_ELEMENT {
+    $$ = cr("abstract class xhp_");
   }
 ;
 

xhp_scanner.l

@@ -314,8 +314,8 @@ B b?
       return tok(t_HEREDOC);
     } else {
       ++yylloc->actual_line_offset;
+      yyextra->heredoc_data_last = yytext + yyleng;
       yymore();
-      BEGIN(HEREDOC_DATA);
     }
   }
   [^\r\n]+ {
@@ -324,8 +324,8 @@ B b?
   }
   {NEWLINE} {
     ++yylloc->actual_line_offset;
+    yyextra->heredoc_data_last = yytext + yyleng;
     yymore();
-    BEGIN(HEREDOC_LINE_START);
   }
 }
 <HEREDOC_DATA>{
@@ -348,7 +348,7 @@ B b?
   ">" return tok(t_XHP_GREATER_THAN);
 }
 <XHP_LABEL>{
-  " " {
+  {WHITESPACE} {
     flex_pop_state(yyg);
     return tok(t_XHP_WHITESPACE);
   }