Backport SQLite memcmp patch.

third_party/sqlite/src/src/expr.c

Index: third_party/sqlite/src/src/expr.c
diff --git a/third_party/sqlite/src/src/expr.c b/third_party/sqlite/src/src/expr.c
index 2699ae1cfd48ff483fcf317a82a982daa6a8bdfb..9d1193b35825ff7ea5b10d9e391ca425a1771840 100644
--- a/third_party/sqlite/src/src/expr.c
+++ b/third_party/sqlite/src/src/expr.c
@@ -578,12 +578,10 @@ void sqlite3ExprAssignVarNumber(Parse *pParse, Expr *pExpr){
     ** has never appeared before, reuse the same variable number
     */
     int i;
-    u32 n;
-    n = sqlite3Strlen30(z);
     for(i=0; i<pParse->nVarExpr; i++){
       Expr *pE = pParse->apVarExpr[i];
       assert( pE!=0 );
-      if( memcmp(pE->u.zToken, z, n)==0 && pE->u.zToken[n]==0 ){
+      if( strcmp(pE->u.zToken, z)==0 ){
         pExpr->iColumn = pE->iColumn;
         break;
       }