Ошибка "Type mismatch in redeclaration of" при компиляции примера подключения OpenGL

//---------------------------------------------------------------------------
 
#include <vcl.h>
#pragma hdrstop
 
#include "Unit1.h"
#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glaux.h>
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
    : TForm(Owner)
{
}
void FormResize(TObject *Sender);
BOOL bSetupPixelFormat(HDC hdc);
HGLRC wglCreateContext(HDC hdc);
BOOL wglMakeCurrent(HDC hdc, HGLRC hglrc);
 
void __fastcall TForm1::FormClose(TObject *Sender, TCloseAction & Action)
{
        if(ghRC)
        {
          wglMakeCurrent(ghDC,0);
          wglDeleteContext(ghRC);
        }
        if(ghDC)
          ReleaseDC(Handle, ghDC);
}
 
void FormResize(TObject *Sender)
{
    glViewport( 0, 0, Width, Height );
    glMatrixMode( GL_PROJECTION );
    glLoadIdentity();
    glOrtho(-5,5, -5,5, 2,12);
    gluLookAt(0,0,5, 0,0,0, 0,1,0);
    glMatrixMode( GL_MODELVIEW );
}
 
void __fastcall TForm1::FormCreate(TObject *Sender)
{
         ghDC = GetDC(Handle);
         if (!bSetupPixelFormat(ghDC))
            Close();
         ghRC = wglCreateContext(ghDC);
         wglMakeCurrent(ghDC, ghRC);
         glClearColor(0.0, 0.0, 0.0, 0.0);
         FormResize(Sender);
         glEnable(GL_COLOR_MATERIAL);
         glEnable(GL_DEPTH_TEST);
         glEnable(GL_LIGHTING);
         glEnable(GL_LIGHT0);
           float p[4]={3,3,3,1},
                 d[3]={-1,-1,-3};
         glLightfv(GL_LIGHT0,GL_POSITION,p);
         glLightfv(GL_LIGHT0,GL_SPOT_DIRECTION,d);
}
 
BOOL bSetupPixelFormat(HDC hdc)
      {
          PIXELFORMATDESCRIPTOR pfd, *ppfd;
          int pixelformat;
          ppfd = &pfd;
          ppfd->nSize = sizeof(PIXELFORMATDESCRIPTOR);
          ppfd->nVersion = 1;
          ppfd->dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER;
          ppfd->dwLayerMask = PFD_MAIN_PLANE;
          ppfd->iPixelType = PFD_TYPE_RGBA;
          ppfd->cColorBits = 16;
          ppfd->cDepthBits = 16;
          ppfd->cAccumBits = 0;
          ppfd->cStencilBits = 0;
          if ((pixelformat = ChoosePixelFormat(hdc, ppfd)) == 0)
          {
              MessageBox(NULL, "ChoosePixelFormat failed", "Error",
        MB_OK);
              return FALSE;
          }
          if (SetPixelFormat(hdc, pixelformat, ppfd) == FALSE)
          {
              MessageBox(NULL, "SetPixelFormat failed", "Error",
        MB_OK);
              return FALSE;
          }
          return TRUE;
      }
//---------------------------------------------------------------------------
void __fastcall TForm1::Timer1Timer(TObject *Sender)
{
                  Draw();
}
//---------------------------------------------------------------------------
      void TForm1.Draw()
      {
        glClear(GL_DEPTH_BUFFER_BIT xor GL_COLOR_BUFFER_BIT);
        GLUquadricObj *quadObj;
        quadObj:=gluNewQuadric();
        gluQuadricDrawStyle(quadObj, GLU_FILL);
        glColor3f(1,0,0);
        gluSphere(quadObj, 2,10,10);
          glRotatef(3, 0,1,0);
        gluDeleteQuadric(quadObj);
        SwapBuffers(ghDC);
      }

//---------------------------------------------------------------------------
 
#ifndef Unit1H
#define Unit1H
//---------------------------------------------------------------------------
#include <System.Classes.hpp>
#include <Vcl.Controls.hpp>
#include <Vcl.StdCtrls.hpp>
#include <Vcl.Forms.hpp>
#include <Vcl.ExtCtrls.hpp>
//---------------------------------------------------------------------------
class TForm1 : public TForm
{
__published:    // IDE-managed Components
    TTimer *Timer1;
    void __fastcall Timer1Timer(TObject *Sender);
private:    // User declarations
    HGLRC ghRC;
    HDC   ghDC;
    void Draw();
public:     // User declarations
    __fastcall TForm1(TComponent* Owner);
};
//---------------------------------------------------------------------------
extern PACKAGE TForm1 *Form1;
//---------------------------------------------------------------------------
#endif

HGLRC wglCreateContext(HDC hdc);
BOOL wglMakeCurrent(HDC hdc, HGLRC hglrc);

__published:    // IDE-managed Components
    void __fastcall FormClose(TObject *Sender, TCloseAction &Action);