- A few fixes to ensure SimGear compiles again on cygwin.

* on cygwin, isnan is declared in ieeepf.h
  * CYGWIN is a special case in that it is windows based, but sometimes
    folows unix conventions. SGAtomic compilation failed on an illegal
    volatile type cast without the additional __CYGWIN__ define check.

simgear/math/SGVec2.hxx

@@ -18,6 +18,10 @@
 #ifndef SGVec2_H
 #define SGVec2_H
 
+#if defined ( __CYGWIN__ )
+#include <ieeefp.h>
+#endif
+
 #include <osg/Vec2f>
 #include <osg/Vec2d>
 

simgear/scene/material/matlib.cxx

@@ -33,6 +33,10 @@
 #  include <windows.h>
 #endif
 
+#if defined ( __CYGWIN__ )
+#include <ieeefp.h>
+#endif
+
 #include <simgear/compiler.h>
 #include <simgear/constants.h>
 #include <simgear/structure/exception.hxx>

simgear/scene/sky/sphere.cxx

@@ -20,6 +20,9 @@
 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 //
 // $Id$
+#ifdef __CYGWIN__
+#include <ieeefp.h>
+#endif
 
 
 #include <simgear/compiler.h>

simgear/scene/sky/stars.cxx

@@ -27,6 +27,10 @@
 #  include <simgear_config.h>
 #endif
 
+#ifdef __CYGWIN__
+#include <ieeefp.h>
+#endif
+
 #include <simgear/compiler.h>
 #include <simgear/constants.h>
 #include <simgear/debug/logstream.hxx>

simgear/structure/SGAtomic.hxx

@@ -28,7 +28,7 @@
 #elif defined(__sgi) && defined(_COMPILER_VERSION) && (_COMPILER_VERSION>=730)
 // No need to include something. Is a Compiler API ...
 # define SGATOMIC_USE_MIPSPRO_BUILTINS
-#elif defined(WIN32) 
+#elif defined(WIN32)  && !defined ( __CYGWIN__ )
 # include <windows.h>
 # define SGATOMIC_USE_WIN32_INTERLOCKED
 #else