GL_UNSIGNED_SHORT_5_6_5 undeclared?

I have a problem loading a texture using SDL library.

Usually I make programs on Linux but I try to create a code that is compatible with Visual Studio also. On Linux are everything OK but on Visual Studio it crashes in "GL_UNSIGNED_SHORT_5_6_5" in the glTexImage2D(...) function.

Below is a general idea about what i want to do which I inspired by this tutorial:

#include "stdafx.h"
#include <stdlib.h>
#include <stdio.h>
#include <GL/glut.h>
//#include <GL/glext.h> 
#include "SDL.h"

int brick;
float c=0.5;
float rx_min=0, ry_min=0;
float rx_max=1, ry_max=1;

unsigned int LoadTexture(const char* filename);
void DrawTexture(int object);
void setupmywindow();
void myDrawing();


void setupmywindow()
{
    glClearColor(1.0,1.0,1.0,0);  
    glColor3f(0.0, 0.0, 0.0);     
    glPolygonMode(GL_FRONT_AND_BACK,GL_FILL);
    gluOrtho2D(rx_min,ry_min, rx_max, ry_max);  
    brick = LoadTexture("brick.bmp");
}

void DrawTexture(int object)
{
    glBindTexture(GL_TEXTURE_2D, object);
    glColor3f(c,c,c);
    glBegin(GL_QUADS);
        glTexCoord2f(0., 1. );
        glVertex2f( rx_min , ry_min );
        glTexCoord2f(0., 0. );
        glVertex2f( rx_min, ry_max );
        glTexCoord2f(1., 0. );
        glVertex2f( rx_max , ry_max );
        glTexCoord2f(1., 1. );
        glVertex2f( rx_max , ry_min );
    glEnd();
}
unsigned int LoadTexture(const char* filename)
{
    SDL_Surface* img=SDL_LoadBMP(filename);
    unsigned int id;
    glGenTextures(1, &id);
    glBindTexture(GL_TEXTURE_2D,id);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, img->w, img->h, 0, GL_RGB, GL_UNSIGNED_SHORT_5_6_5, img->pixels);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    SDL_FreeSurface(img);
    return id;
}

void myDrawing()
{    
    glClear(GL_COLOR_BUFFER_BIT);   
    DrawTexture(brick);

    glFlush();

}

int main(int argc, char **argv)
{

    printf("AUTH Computational Physics - Computer Graphics\n");
    printf("Project >>TestTexture.cpp\n");
    printf("--------------------------------------------------------\n");

    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB); 
    glutInitWindowPosition(50,50);
    glutCreateWindow("Texture Test");

    setupmywindow();        
    glutDisplayFunc(myDrawing);  

    glutMainLoop();

    return 0;
}

The error is:

error C2065: 'GL_UNSIGNED_SHORT_5_6_5' : undeclared identifier

Here is the image that I try to load and it is configured as a bitmap (8bit 5 6 5) with GIMP 2.8

NOTE: When I uncoment #include < GL/glext.h > which is not needed on Linux, I get the above message: Unhandled exception at 0x00d1193f in testTesxture.exe: 0xC0000005: Access violation reading location 0x00000014.

Generally if I save a bitmap image (for example with paint) how can I uderstand the type I have to put (GL_UNSIGNED_SHORT_5_6_5, GL_UNSIGNED_BYTE etc)?

The problem is likely that Windows uses an older version of OpenGL than Linux, and this old OpenGL version does not have that specific identifier (and others, I'm sure). To get around this and any other possible version problems, I would use GLEW which does the hard work for you.