Fix compilation errors and C++-style fixes

[zhao-shihan]

Compilation issues:

1. M_PI is a non-standard feature. Standard C++ library does not guarantee M_PI definition. As a header-only library, this corner case should be covered.
2. Bare cout and endl are not available unless there is a using namespace std. Add std:: before both of them to fix this issue.
3. std::cout and std::endl are not available unless iostream is included.

Potential issues and C++ style fixing:

1. Include cmath instead of math.h.
2. C++ integer type aliases should have std:: qualification. Bare uint64_t, size_t and etc. is C-styled code, not C++.

[dr4kan]

Merging fix for compilation issues