configure: add missing AM_CONDITIONAL call
configure: Add tests for dsound and d3d9
configure: Remove some CONFIG_ variables, rename to HAVE_
configure: Support OSS, X11, X11 OpenGL and Xv

Xv is untested as I don't have it installed (it's not packaged on cygwin).
configure: rename remaining CONFIG_GL_WIN32 to HAVE_OPENGL_WIN32

Fixes opengl on windows after the previous commit.