commit dd5550b9df5da33401997386d2d3e6af3bb6f3c2
Author: Olli Pottonen <olli pottonen iki fi>
Date:   Tue Jul 7 23:26:27 2015 +1000

    Require whitespace after '<!DOCTYPE'

diff --git a/parser.c b/parser.c
index fe603ac..d8c3ee3 100644
--- a/parser.c
+++ b/parser.c
@@ -8326,6 +8326,10 @@ xmlParseDocTypeDecl(xmlParserCtxtPtr ctxt) {
      * We know that '<!DOCTYPE' has been detected.
      */
     SKIP(9);
+    if (!IS_BLANK_CH(CUR)) {
+      xmlFatalErrMsg(ctxt, XML_ERR_SPACE_REQUIRED,
+		     "Space required after '<!DOCTYPE'\n");
+    }
 
     SKIP_BLANKS;