consistent ordering of AC_MSG, additional library checks and var-setting.
also, use "=" rather than "=" when testing for equality

CPPFLAGS are needed to compile rtaudio.
these are not the same flags as needed for compiling an application using rtaudio.
sometimes this is even harmful.

Closes: https://github.com/thestk/rtaudio/issues/103

Signed-off-by: IOhannes m zmölnig <zmoelnig@umlautQ.umlaeute.mur.at>

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.

Fixes #100.

add rtaudio c api wrappers

Fix AC_ARG_WITH usage to be like the manual suggests:
https://autotools.io/autoconf/arguments.html

a JACK-specific flag to disable automatic connection of ports

Add mmsystem.h and mmreg.h for dsound.

Closes #39

Closes #80

Closes #86

C++0x compatible exception semantics: remove throw()

Fixes #91.

Fix some warnings in the tests in Visual Studio

Added interpolation to WASAPI's sample rate converter