Changes to get SimGear to configure and compile out-of-the-box on

a MinGW target:

Link against alut.dll in addition to openal32.dll.

Remove some preprocessor defines from compiler.h that were
confusing the mingw and/or libstdc++ headers (I put the _isnan
one back in the only file it was used).

Hack a broken sleep() call into the OpenAL sample programs so
that they will compile (but not work) in a non-POSIX environment.

Change the header file ordering in sample_openal.hxx to get
around some really weird interactions between MinGW's windows.h
and the gcc iostream header.

configure.ac

@@ -275,7 +275,7 @@ case "${host}" in
 *-*-cygwin* | *-*-mingw32*)
     dnl CygWin under Windoze.
 
-    LIBS="$LIBS -lopenal32 -lwinmm -ldsound -ldxguid -lole32"
+    LIBS="$LIBS -lalut -lopenal32 -lwinmm -ldsound -ldxguid -lole32"
     ;;
 
 *-apple-darwin*)