Use separate Ragel machines for script/style tags

Previously a single Ragel machine was used for processing HTML
script and style tags. This had the unfortunate side-effect that the
following was not parsed correctly (while being valid HTML):

    <script>
    var foo = "</style>";
    </script>

The same applied to style tags:

    <style>
    /* </script> */
    </style>

By using separate machines we can work around the above issue. The
downside is that this can produce multiple T_TEXT nodes, which have to
be stitched back together in the parser.

ext/c/lexer.rl

@@ -19,11 +19,15 @@ on `ts` and `te`) so the macro ignores this argument.
 #define advance_line(amount) \
     rb_funcall(self, id_advance_line, 1, INT2NUM(amount));
 
-#define literal_html_element_p() \
-    rb_funcall(self, id_literal_html_element_p, 0) == Qtrue
+#define html_script_p() \
+    rb_funcall(self, id_html_script_p, 0) == Qtrue
+
+#define html_style_p() \
+    rb_funcall(self, id_html_style_p, 0) == Qtrue
 
 ID id_advance_line;
-ID id_literal_html_element_p;
+ID id_html_script_p;
+ID id_html_style_p;
 ID id_html;
 
 %%machine c_lexer;
@@ -183,9 +187,10 @@ void Init_liboga_xml_lexer()
     VALUE mXML   = rb_const_get(mOga, rb_intern("XML"));
     VALUE cLexer = rb_define_class_under(mXML, "Lexer", rb_cObject);
 
-    id_advance_line           = rb_intern("advance_line");
-    id_literal_html_element_p = rb_intern("literal_html_element?");
-    id_html                   = rb_intern("html");
+    id_advance_line  = rb_intern("advance_line");
+    id_html_script_p = rb_intern("html_script?");
+    id_html_style_p  = rb_intern("html_style?");
+    id_html          = rb_intern("html");
 
     rb_define_method(cLexer, "advance_native", oga_xml_lexer_advance, 1);
     rb_define_method(cLexer, "reset_native", oga_xml_lexer_reset, 0);