Merge FreeBSD patches.

Taken from:
http://svnweb.freebsd.org/ports/head/devel/simgear/files/

CMakeLists.txt

@@ -276,12 +276,12 @@ SET(CMAKE_MINSIZEREL_POSTFIX "" CACHE STRING "add a postfix, usually empty on wi
 # isnan might not be real symbol, so can't check using function_exists
 check_cxx_source_compiles(
     "#include <cmath> 
-    void f() { isnan(0.0);} "
+    int main() { return isnan(0.0);} "
     HAVE_ISNAN)
 
 check_cxx_source_compiles(
     "#include <cmath> 
-    void f() { std::isnan(0.0);} "
+    int main() { return std::isnan(0.0);} "
     HAVE_STD_ISNAN)
 
 if(CMAKE_COMPILER_IS_GNUCXX)

simgear/canvas/ShivaVG/src/shDefs.h

@@ -156,7 +156,7 @@ SHfloat getMaxFloat();
 
 /* OpenGL headers */
 
-#if defined(VG_API_LINUX)
+#if defined(VG_API_LINUX) || defined(VG_API_FREEBSD)
     #include <GL/gl.h>
     #include <GL/glx.h>
 #elif defined(VG_API_MACOSX)

simgear/debug/BufferedLogCallback.cxx

@@ -26,6 +26,8 @@
 #include <simgear/sg_inlines.h>
 #include <simgear/threads/SGThread.hxx>
 #include <simgear/threads/SGGuard.hxx>
+
+#include <cstdlib> // for malloc
      
 namespace simgear
 {