code cleanup: move check for SSML comments and declarations to

ProcessSsmlTag()

Note the line in readclause.c:
if ((c2 == '/') || iswalpha(c2) || c2 == '!' || c2 == '?') {

It might be enough to pass everything to ProcessSsmlTag. What are the
cases that are skipped because of this?

src/libespeak-ng/readclause.c

 				if ((c1 <= 0x20) && ((sayas_mode == SAYAS_SINGLE_CHARS) || (sayas_mode == SAYAS_KEY)))
 					c1 += 0xe000; // move into unicode private usage area
 			} else if ((c1 == '<') && (ssml_ignore_l_angle != '<')) {
-				if ((c2 == '!') || (c2 == '?')) {
-					// a comment, ignore until closing '<'  (or <?xml tag )
-					while (!Eof() && (c1 != '>'))
-						c1 = GetC();
-					c2 = ' ';
-				} else if ((c2 == '/') || iswalpha(c2)) {
+				if ((c2 == '/') || iswalpha(c2) || c2 == '!' || c2 == '?') {
 					// check for space in the output buffer for embedded commands produced by the SSML tag
 					if (ix > (n_buf - 20)) {
 						// Perhaps not enough room, end the clause before the SSML tag

src/libespeak-ng/ssml.c

 	PARAM_STACK *sp;
 	SSML_STACK *ssml_sp;
 
+	// don't process comments and xml declarations
+	if (wcsncmp(xml_buf, (wchar_t *) "!--", 3) == 0 || wcsncmp(xml_buf, (wchar_t *) "?xml", 4) == 0) {
+		return 0;
+		}
+
 	// these tags have no effect if they are self-closing, eg. <voice />
 	static char ignore_if_self_closing[] = { 0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 0, 1, 0, 1, 0, 0, 0, 0 };