Merge pull request #152 from aluaces/spelling2

Some spelling fixes in comments.

src/osg/GL.in

@@ -43,7 +43,7 @@
 
 #ifndef WIN32
 
-    // Required for compatibility with glext.h sytle function definitions of
+    // Required for compatibility with glext.h style function definitions of
     // OpenGL extensions, such as in src/osg/Point.cpp.
     #ifndef APIENTRY
         #define APIENTRY

src/osg/TextureBuffer.cpp

@@ -138,7 +138,7 @@ void TextureBuffer::apply(State& state) const
 
     TextureObject* textureObject = getTextureObject(contextID);
 
-///This code could be usefull but would require to watch BufferData changes
+///This code could be useful but would require to watch BufferData changes
 ///perhaps a mutable percontext dirtyflag (all reset to true onTextureObjectChanged) would do the trick
 #if 0
    if (textureObject)