Use explicit call to std math.

[beskidlabs]

Using the lib in embedded environments, causes issues with compilation using ARM embedded toolchains. The call to round() is being resolved as a call to lround() and hence breaks the build, as std::max() expects two arguments of type double. Making it a explicit call to std::round() fixes the issue.

[google-cla]

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[wowo68]

这是来自QQ邮箱的假期自动回复邮件。你好，我最近正在休假中，无法亲自回复你的邮件。我将在假期结束后，尽快给你回复。

[beskidlabs]

Well, I don't want to go through all that formalities (I don't have nor want to have a google account) just to submit such a miniscule change, perhaps it's better if I submit it via issue tracking system..