0025213: Visualization, TKOpenGl - do not use deprecated built-ins in GLSL shaders

Inherit NCollection_Buffer from Standard_Transient, do not use incomplete NCollection_Handle.

OpenGl_Context, add methods ActiveProgram(),BindProgram()
to manage currently active GLSL program.
Add method ::ToUseVbo().

OpenGl_ShaderProgram, setup locations of pre-defined vertex attributes
occVertex, occNormal, occTexCoord, occColor before linkage.
Remove methods OpenGl_ShaderProgram::Bind(), ::BindWithVariables()
and ::Unbind() - OpenGl_Context::BindProgram() should be used instead.

Introduce class OpenGl_VertexBufferCompat, which emulates VBO
behavior on systems without VBO (compatibility with broken OpenGL drivers on Windows).

OpenGl_PrimitiveArray - use OpenGl_VertexBufferCompat when VBO is unavailable,
remove duplicated code. Use OpenGl_VertexBuffer::HasNormalAttribute()
method to activate lighting.

OpenGl_Text - use OpenGl_VertexBufferCompat, eliminate duplicated code.

Changes in OpenGl_VertexBuffer, drop methods BindFixed()/UnbindFixed().
Superseded by new methods BindAllAttributes()/UnbindAllAttributes()
which handle active GLSL program, when it is set.

src/Shaders/Declarations.glsl

@@ -23,10 +23,10 @@
 // vertex attributes from compatibility profile. In the next
 // release old functionality will be removed from shader API.
 #ifdef VERTEX_SHADER
-  #define occColor    gl_Color          //!< Vertex color
-  #define occNormal   gl_Normal         //!< Normal  coordinates
-  #define occVertex   gl_Vertex         //!< Vertex  coordinates
-  #define occTexCoord gl_MultiTexCoord0 //!< Texture coordinates
+  attribute vec4 occVertex;
+  attribute vec3 occNormal;
+  attribute vec4 occTexCoord;
+  attribute vec4 occColor;
 #endif
 
 // Matrix state

src/Shaders/RaytraceBase.vs

@@ -1,12 +1,12 @@
-in vec4 aPosition;
+in vec4 occVertex;
 
 //! Normalized pixel coordinates.
 out vec2 vPixel;
 
 void main (void)
 {
-  vPixel = vec2 ((aPosition.x + 1.f) * 0.5f,
-                 (aPosition.y + 1.f) * 0.5f);
-                 
-  gl_Position = aPosition;
-}
+  vPixel = vec2 ((occVertex.x + 1.f) * 0.5f,
+                 (occVertex.y + 1.f) * 0.5f);
+
+  gl_Position = occVertex;
+}