修改UISearchBar搜索框的高度（UISearchBar-

新建一个类继承自UISearchBar
然后在.m文件中实现：

- (void)layoutSubviews{
    [super layoutSubviews];
    for (UIView*view in self.subviews) {
        for (UIView*subView in view.subviews) {
            if ([subView isKindOfClass:[UITextField class]]) {
                //你想要设置的高度
                subView.frame = CGRectMake(5, 3, self.w-10, self.h-6);
            }
        }
    }
}