DirectXTK emits a -Wreserved-identifier warning with clang v13

[Chuck Walbourn]

Officially _ followed by a capital letter is reserved by the C++ Standard for implementors of the compiler and library. Clang v13 adds a new warning to detect this case.

_IsWIC2
_GetWIC
_WICToDXGI
_WICBitsPerPixel

Also fix

Audio\WaveBankReader.cpp(546,10): warning: variable 'wait' set but not used [-Wunused-but-set-variable]