From Fredric Mammond, fix for build using full extension checked mechansim

include/osg/BlendEquation

@@ -18,11 +18,11 @@
 
 #ifndef GL_VERSION_1_2
 /* Logic Ops */
-#define GL_MIN_EXT				0x8007
-#define GL_MAX_EXT				0x8008
-#define GL_FUNC_ADD_EXT				0x8006
-#define GL_FUNC_SUBTRACT_EXT			0x800A
-#define GL_FUNC_REVERSE_SUBTRACT_EXT		0x800B
+#define GL_MIN					0x8007
+#define GL_MAX					0x8008
+#define GL_FUNC_ADD				0x8006
+#define GL_FUNC_SUBTRACT			0x800A
+#define GL_FUNC_REVERSE_SUBTRACT		0x800B
 #define GL_ALPHA_MIN_SGIX			0x8320
 #define GL_ALPHA_MAX_SGIX			0x8321
 #define GL_LOGIC_OP				0x0BF1
@@ -86,11 +86,54 @@ class SG_EXPORT BlendEquation : public StateAttribute
         inline GLenum getEquation() const { return _equation; }
         
         virtual void apply(State& state) const;
+        /** Encapsulates queries of extension availability, obtains extension
+          * function pointers, and provides convinience wrappers for
+          * calling extension functions. */        
+        class SG_EXPORT Extensions : public osg::Referenced
+        {
+            public:
+                Extensions();
+
+                Extensions(const Extensions& rhs);
+                
+                void lowestCommonDenominator(const Extensions& rhs);
+                
+                void setupGLExtenions();
+
+                void setBlendEquationSupported(bool flag) { _isBlendEquationSupported=flag; }
+                bool isBlendEquationSupported() const { return _isBlendEquationSupported; }
+                
+                void setBlendEquationProc(void* ptr) { _glBlendEquation = ptr; }
+                void glBlendEquation(GLenum mode) const;
+
+            protected:
+
+                ~Extensions() {}
+                
+                bool    _isBlendEquationSupported;
+
+                void*   _glBlendEquation;
+
+        };
+        
+        /** Returns the Extensions object for the given context.
+          * If createIfNotInitalized is true and the Exentsions object doesn't
+          * exist, getExtensions() creates it on the given context.
+          * Returns NULL if createIfNotInitalized is false and the Extensions
+          * object doesn't exist. */
+        static Extensions* getExtensions(unsigned int contextID,bool createIfNotInitalized);
+
+        /** setExtensions() allows users to override the extensions across graphics contexts.
+          * Typically used when you have different extensions supported across graphics pipes,
+          * but need to ensure that they all use the same low common denominator extensions. */
+        static void setExtensions(unsigned int contextID,Extensions* extensions);
+
 
     protected :
 
         virtual ~BlendEquation();
 
+
         GLenum _equation;
 };