Support for MSVC

[Hizuru3]

close #9

Note that this PR introduces a new typedef cc_max_align_t and a function-like macro CC_UNREACHABLE(). Compiler specific optimizations are also added to cc_first_nonzero_uint16() and cc_last_nonzero_uint16().

By using MSVC 19.39 or later, you can compile with either option of /std:c11, /std:c17 or /std:clatest for C. In the case of C++, the /Zc:preprocessor option must be specified.