MXS-2431 Recognize the XA keyword

Recognize the XA keyword and classify the statement as write.
Needs to be dealt with explicitly as sqlite3 assumes there are
no keywords starting with the letter X.

query_classifier/qc_sqlite/sqlite-src-3110100/src/parse.y

@@ -639,6 +639,7 @@ columnid(A) ::= nm(X). {
   VALUE VIEW /*VIRTUAL*/
   /*WITH*/
   WORK
+  XA
 %endif
   .
 %wildcard ANY.

query_classifier/qc_sqlite/sqlite-src-3110100/src/tokenize.c

@@ -626,6 +626,22 @@ int sqlite3GetToken(const unsigned char *z, int *tokenType){
       /* If it is not a BLOB literal, then it must be an ID, since no
       ** SQL keywords start with the letter 'x'.  Fall through */
     }
+#endif
+#ifdef MAXSCALE
+    // It may be the "XA" keyword.
+    // If the next character is 'a' or 'A', followed by whitespace or a
+    // comment, then we are indeed dealing with the "XA" keyword.
+    if (( z[1]=='a' || z[1]=='A' ) &&
+        (sqlite3Isspace(z[2]) ||                              // Whitespace
+         (z[2]=='/' && z[3]=='*') ||                          // Beginning of /* comment
+         (z[2]=='#') ||                                       // # eol comment
+         (z[2]=='-' && z[3]=='-' && sqlite3Isspace(z[4])))) { // --  eol comment
+      extern int maxscaleKeyword(int);
+
+      *tokenType = TK_XA;
+      maxscaleKeyword(*tokenType);
+      return 2;
+    }
 #endif
     case CC_ID: {
       i = 1;