closes bpo-38174: Update vendored expat library to 2.2.8. (GH-16346)

Fixes CVE-2019-15903. See full changelog at https://github.com/libexpat/libexpat/blob/R_2_2_8/expat/Changes.
diff --git a/Modules/expat/xmlrole.h b/Modules/expat/xmlrole.h
index e5f048e..036aba6 100644
--- a/Modules/expat/xmlrole.h
+++ b/Modules/expat/xmlrole.h
@@ -36,7 +36,7 @@
 #ifdef __VMS
 /*      0        1         2         3      0        1         2         3
         1234567890123456789012345678901     1234567890123456789012345678901 */
-#define XmlPrologStateInitExternalEntity    XmlPrologStateInitExternalEnt
+#  define XmlPrologStateInitExternalEntity XmlPrologStateInitExternalEnt
 #endif
 
 #include "xmltok.h"
@@ -113,11 +113,8 @@
 };
 
 typedef struct prolog_state {
-  int (PTRCALL *handler) (struct prolog_state *state,
-                          int tok,
-                          const char *ptr,
-                          const char *end,
-                          const ENCODING *enc);
+  int(PTRCALL *handler)(struct prolog_state *state, int tok, const char *ptr,
+                        const char *end, const ENCODING *enc);
   unsigned level;
   int role_none;
 #ifdef XML_DTD
@@ -132,8 +129,8 @@
 void XmlPrologStateInitExternalEntity(PROLOG_STATE *);
 #endif /* XML_DTD */
 
-#define XmlTokenRole(state, tok, ptr, end, enc) \
- (((state)->handler)(state, tok, ptr, end, enc))
+#define XmlTokenRole(state, tok, ptr, end, enc)                                \
+  (((state)->handler)(state, tok, ptr, end, enc))
 
 #ifdef __cplusplus
 }