Thanks github user @bontric, closes #113.

Warnings/errors "unused function" are from the unicode conversion
functions on Windows, and "unused but set variable" is from ASIO
source code; we disable these warnings on Windows builds.

Revert "fix" for Issue #69

Similar to edb4ec67.  The reason is because std::roundf causes errors
in some compilers even with cmath, yet roundf by itself should exist
in math.h.  TODO: Switch to std::round when moving to C++11.

Closes #39

Closes #80

The check if ( subdevice != -1 ) was being done on a potentially
uninitialized variable.

Use free() for allocated memory by calloc (not delete).
Deleting calloc-ed memory will become problem in the environment which
overrides global "operator delete" like some game engine.

Without algorithm header, Visual Studio complaints that std::max is not
declared and defined.
Including algorithm header resolves this issue.