Major check-in of changes for GL_EXT_framebuffer_object extension.

Main driver impacts:
- new code for creating the Mesa GLframebuffer
- new span/pixel read/write code
Some drivers not yet updated/tested.

src/mesa/main/bufferobj.c

@@ -900,7 +900,7 @@ _mesa_GetBufferParameterivARB(GLenum target, GLenum pname, GLint *params)
 
    switch (pname) {
       case GL_BUFFER_SIZE_ARB:
-         *params = bufObj->Size;
+         *params = (GLint) bufObj->Size;
          break;
       case GL_BUFFER_USAGE_ARB:
          *params = bufObj->Usage;