Minor changes to silence some compiler warnings with MSVC.

FossilOrigin-Name: 4927c62d6214d93e582bf1266215ed3519630c15

src/vdbe.c

@@ -538,7 +538,7 @@ static int checkSavepointCount(sqlite3 *db){
 int sqlite3VdbeExec(
   Vdbe *p                    /* The VDBE */
 ){
-  int pc;                    /* The program counter */
+  int pc=0;                  /* The program counter */
   Op *aOp = p->aOp;          /* Copy of p->aOp */
   Op *pOp;                   /* Current operation */
   int rc = SQLITE_OK;        /* Value to return */